John Bantin has been a full-time professional diving writer and underwater photographer since 1990. He makes around 300 dives each year testing diving equipment.

When it comes to breathing, we all take things very seriously. So it's no surprise that some people are willing to spend top dollar on a regulator.
     The challenge can be for manufacturers to find a justification for charging top dollar. One way is to eschew the use of chromed brass and use another, more expensive, metal.
     Atomic, in the USA, was the first company to offer a spectacularly expensive all-titanium regulator, followed by Mares with the Ti Planet. Now Scubapro has got in on the act.
     I have been testing its MK25 Titanium/S600T, which breathes exactly the same as the superb, top-performing piston-type MK20/S600 that I have covered before.
     I used the MK25 Titanium at Cocos Island, and in the canyon at Roca Suceo found myself hooked on at 30m with such a force of water flowing over me that I became wrapped in the tight embrace of my camera and its two flashguns.
     With the camera pressed to my chest, the flashgun arms then folded back on themselves and on me, like some medieval instrument of torture, giving me no chance to get a picture.
     It was a moment for the other divers present to savour. However, the regulator behaved impeccably, with no hint of the free-flow so often encountered with other models in such extreme circumstances.
     Titanium provides light weight combined with strength and an almost gold-like resistance to corrosion. But didn't Scubapro achieve that with the all-aluminium MK20 UL?
     Well, if you read my test report of that model you'll know that I dismayed Scubapro by telling Diver readers tales of corrosion caused by electrolysis between the aluminium of the UL regulator and the chromed brass of the hose ends screwed into it.
     I recently witnessed someone struggling to undo the A-clamp screw of theirs from its aluminium yoke - with the help of a vice.
     I also reported incidences of A-clamps being snapped off by rough handling, for example when fully rigged tanks fell out of racks on boats during rough weather.
     The people at Scubapro denied at the time that this might be the case, but they have now introduced the MK25 TI Alloy, which is made of aluminium but has titanium parts where the problem areas used to be, and plastic buffers that go between any chromed brass hose-fittings that you might use. I rest my case.
     The TI Alloy's outer aluminium parts have a blue coating with a rubbery feel. It is cheaper than "all-titanium" and makes this regulator lighter than almost any I have tried.
     The slightly heavier MK25 TI Titanium goes all the way, in that its metal parts are made entirely from titanium (apart from the original stainless-steel piston and spring).
     Both use the S600 second stage, the metal parts of which are titanium, and both regulators have masses of dive-store appeal. With the first in metallic blue and the second in gunmetal grey, they look the business.
     Of course light weight offers no real advantage in the water, as you have to make up weight lost with extra lead, but it certainly is attractive when packing a bag for a weight-restricted flight.
     Scubapro has pursued the piston-design ideal with most of its regulators, whereas other manufacturers all seem to use diaphragm designs for their top performers. Piston regulators used to have the advantage of being easy to service, especially in far-off places, which is why you will see so many divers taking Scubapro regulators abroad with them.
     The MK20 and MK25 are the acme of achievement in performance with this type of regulator, though, as with many products that started life simply (the original Porsche car comes to mind), these regulators have become really complex.
     That said, if you are like me and concerned mainly with what happens under water, you can enjoy the best and let the Scubapro service technician worry about the other stuff!
     One last point. Neither regulator is recommended for use with nitrox, as titanium is not a comfortable bedfellow when there are high levels of oxygen in the mix.
The MK25 Titanium/S600T costs £665 and the MK25 TI Alloy/S600T costs £465.

Melting Milk Tray Man
I have had undersuits that made me look like a Formula One mechanic and others that made me look like La La, but the one sent for test by Fourth Element made me inclined to visit a lady's boudoir with a box of chocolates before I dived into the sea. Milk Tray Man!
     The Xerotherm uses a body-hugging stretchy fabric called Polartec which has the property of wicking away moisture from your skin so that you still feel nice and dry "though you may be sweating bucketfuls".
     And I bet you will be sweating bucketfuls if you combine it with your normal undersuit, as suggested by its maker. It says it's the "ultimate base layer for a drysuit dive".
     The set comprised a long-sleeved top, pants with a drawstring and heel-locating holes, and separate socks. The whole lot fitted me like the proverbial glove and I was snug as a bug in a rug.
     At first I thought the pants had started to come apart at the crotch, but on closer examination of the hole this proved to be a feature aimed, I supposed, at gentlemen.
     But gentlemen would have to be very cold indeed to be able to avail themselves of this facility, such were its dimensions. Then it occurred to me that this was a hole for a tube from a pee-valve to pass through. Silly me! But then, if I am not cold I can go for hours without resorting to such infernal paraphernalia.
     Of course, I used the Xerotherm in conjunction with a lightweight undersuit, but I could foresee times when I would want to use the Fourth Element Technical ensemble alone with a membrane drysuit in a wintry Red Sea, or when I get the chance to drag my own made-to-measure ND neoprene drysuit out from where it languishes in the cupboard.
     This probably sounds wimpish to many of you. Louise Trewavas would no doubt use it to augment her thick 300mg undersuit, but then she rarely dives in water any warmer than frigid and wouldn't get her feet wet unless it involved at least three hours of deco-stops. But then, she's a woman and known to be well Ôard.
     Anyway, I guess that's why they call it "Technical", and Louise is technical. I go diving to have a good time. I suppose wearing something like this, which is both comfortable and doesn't invite ridicule when I'm getting changed behind the Mondeo, goes a long way to helping me pursue my dreams, too.
     It certainly stopped any chafing caused by unplanned folds in the main undersuit getting compressed onto my skin, so I can say that the Fourth Element Technical Xerotherm undersuit was very successful for me.
The Fourth Element Technical Xerotherm as tested (top, pants and socks) costs £116.

Spare the fins, strain the wrists
You might hate finning. It's too much work! But don't think that getting a diver propulsion unit (DPV) is the answer to this problem. Not unless you've got someone always waiting in the water with it ready for you to use.
     That's because anything that weighs enough to equal the amount of water it displaces is bound to be heavy, and a big battery invariably weighs a lot. The man who delivered the SeaScooter Dolphin to my penthouse suite at Eaton Towers one sweaty summer's day can vouch for that. It weighs more than 25kg. We decided that I should try it out at nearby Wraysbury Dive Centre's lake.
     So having charged the unit for the requisite six hours, I persuaded our managing editor Steve to carry it from the car to the water's edge for me. Well, I always insist on being well-rested before a dive!
     The Dolphin is typically American in its design and engineering. It's big and brash, and unsophisticated or even "crude". A large wet battery is contained in the main plastic housing and this powers an electric motor that turns a propeller in a cage below it. The back-plate is removed to get to the battery and ballast and this shuts tight on a thick neoprene gasket with the aid of four cam-catches.
     The diver is towed by means of two grip-handles, one of which has a simple on/off trigger. Three lights tell you the state of charge of the battery.
     The advantage of a lake is its finite dimensions. This would be important if the battery went down. A long walk with a dead DPV is preferable to a long swim with one.
     There was another reason for first trying the Dolphin in a lake. A well-known diving travel agent, trying another make of DPV in the Bahamas and finding that it would not switch off, simply let it go, to wander forever in the infinite ocean. I bet the owners were impressed!
     You can make the Dolphin neutrally buoyant by adding packets of lead shot to the nose section. This is not something that is readily done. You have to remove the battery first, so after that you tend to leave the lead in place. So the Dolphin is a lump. The question was, would it be fun?
     In the water our example proved a little nose-light. In other words, it proved quite an effort to point it downwards to get extra depth.
     On the other hand, it was easy to "climb". This could have been adjusted by adding more weight to the nose section, but as it was perfectly neutrally buoyant as it was, I decided not to adjust for this. Also, it seemed sensible to me to have to struggle to go down, since this added a built-in safety effect.
     Steve and I enjoyed cruising around the lake together. There seemed enough power to tow both of us, even if our progress was more stately than spectacularly fast. When I used it alone, Steve was able to fin alongside me without much effort so I suppose the most speed I made was about half a knot.
     Then we realised that we were producing a veritable vapour trail behind us. This was because the thrust from the propeller was having the same effect on the silty clay bottom as a Kenwood Chef would have on a Readymix cake-mix.
     Our guilt at ruining the viz for other divers was tempered by the need to get the test done, so we constantly re-routed to an undisturbed part of the lake.
     The handles felt as if they flexed and this did not boost my confidence that the unit was unbreakable. I also thought that they were positioned a little too far towards the back of the unit for comfort.
     Riding solo, I was able to stretch my arms out in front and brace the wings of the unit on top of my forearms. Two-up, I really had to be careful how I pointed it so that we went in the right direction.
     I could have done with a depth gauge mounted on the unit. In low viz it's hard to know where you are relative to the surface. I suppose it would be too much to ask for a compensated compass too?
     So we had a fun morning, but I can't say it was without effort. The work of finning was transferred to my wrists, so I still got tired.
     I thought that if I had to journey from the edge of the lake to a work site in the middle each day, it would have been worth having. However, as a toy it represents another thing to need charging, to flood or to go wrong, and it was another large and heavy item that needed loading into the car afterwards. With that in mind, as a diver's toy it's probably more hassle than it's worth.
The SeaScooter Dolphin costs £995.

The great sound of radio snorkel
Lying relaxed on the surface of an azure sea, gently inhaling the odours of the ocean through my snorkel and watching a glitter of fish busying themselves around the flamboyant corals like a myriad of clichés, the disc-jockey broke in with news of freeway delays, followed by an earnest ad for a cream to stop that embarrassing itching.
     That's the problem with local radio. It has to be paid for somehow, and commercial aspects do have a way of intruding.
     Snorkelling is one method of getting away from it all but the Aqua-Lung Tuba FM, a radio snorkel, is a bit of fun for snorkellers who wish to keep part of their brain in the real world.
     An enthusiastic salesman suggested that there was a safety aspect, too: "If a school of man-eating sharks suddenly entered the bay where you were snorkelling, you might hear a warning broadcast," he told me.
     But not before you were part of that news, I'm afraid to say!
     The Tuba FM has an on/off switch, volume control and a station-seeking button. The optimum length for a radio aerial is somewhat longer than that of the average snorkel, so the tube of the Tuba FM bows to the pressures of good reception rather than that of the need to consider carbon dioxide build-up.
     The sound of the programmes is transmitted through your teeth. In the office, people were astounded that they could hear it resonating through my head, but not when I took it from my mouth. However, that will be no surprise to the many of you who assume that my head is as empty as the soundbox of any stringed instrument!
     I enjoy any bit of kit that sparks off a furore of resentment. The Tuba FM caused all sorts of shouts of disapproval from hairy-arsed divers, and Louise in the Diver office, never short of an opinion, said she would rather slit her wrists than be seen with such an item. So I went snorkelling with it.
     Moi? The prince of kit? Snorkelling? With nothing more than basic equipment? Well, yes I did, and I found it very relaxing. I even held my breath a few times and duck-dived to see the fish eye to eye, forsaking radio reception for a moment.
     I did this only a few times, of course. It's far too energetic, especially if you have to clear water from that extra length of tube every time you come up. You need good puff, even though the Tuba FM has an automatic drain valve.
     And then there was the problem of seagulls trying to perch on the end, such was the snorkel's height above the waves.
     No, the Tuba FM is for those who think snorkelling is about lying on the surface and going with the flow. Whether it's relaxing or not depends on what you listen to. If you're in the Bahamas and it's a Sunday morning, you could get an evangelical ear-bashing!
     The Tuba FM costs £169. It uses two AAA batteries and goes through them sooner than you expect, probably because it's easy to leave switched on.