THREE OF US HAD A GREAT DAY OUT at Wraysbury Lake last September. It was an Indian Summer. The water was warm and amazingly clear, probably because it was a Monday and few other divers were there.
We zoomed around, visiting parts of the underwater landscape that I had not seen before. We were trying out some of those diver propulsion vehicles (DPVs) or underwater scooters that are made in China and cost not very much at all.
You cant judge a book by its cover. These Sea-Doo Seascooters may look toy-like compared to the serious-looking DPVs used by cave-divers and the like, but all DPVs are basically a motor and a propeller powered by a battery with an on/off switch, and these three are no exception.
However because they are mass-produced, they are available at prices that almost any diver can afford. You can even buy them in Duty-Free shops at the airport, and take them away with you abroad as carry-on, though I doubt if they would be accepted by Thompsonfly with its 5kg limit! So, at prices between £350 and £600, are they any good
There are seven models in the range but we decided to try only those suitable for divers. The little GTI and VS Supercharged models are rated with a depth-limit of 30m, while the bigger Explorer can be taken safely to 50m. I guess its no accident that the manufacturer chose to name them after cars.
Of course, the bulkier the diver and the equipment to be towed, the slower a DPV will go, but the bulk of the DPV itself also has some bearing on this matter.
Some big, professional-looking DPVs have the aquadynamics of a dustbin and, though they might be powerful, this slows them down.
The little GTI and VS Supercharged models have tiny teardrop-shaped bodies that offer very little forward resistance to the water, and the Explorer isnt much bigger.

THESE SCOOTERS ARE MADE OF PLASTIC, and its undeniable that they look cheap. However, the smaller models have their working electronics well protected by two large O-rings, and the fit is so snug that you are provided with a small air pump for use in forcing the top off, giving access to connect the battery-charger.
Normally, this part is protected by a floodable nose-cone, which houses the buoyancy cell that keeps the nose up. You can always add lead instead if necessary.
The larger Explorer is held together by four large cam-catches and made watertight by two big O-rings. The whole battery-pack lifts out from where it connects via four large push-couplings. It drops down onto a similarly equipped charging chassis that is connected via a small transformer to the mains supply. Its a more precision-made system that accounts for why it costs more than its brothers.
We have tried the basic Seascooter GTI model before. If I remember rightly, my helpmate last time, Nigel, started off by calling it a pile of poop but became more enthusiastic the more he used it. Good news is that its price has reduced since then.
Weighing around 8kg, the GTI has one speed. It has a safety catch and two triggers that need to be operated to make it go, so you stop if you need a hand to clear your ears.
Nevertheless it went well for us - we got a speed of 0.4m/sec from it. This is nothing to be ashamed of, and I am told that a fully charged unit should be good for a two-hour run.
Im not sure my wrists would be strong enough, but it does give the user a good opportunity to cover some territory. The lead-acid battery takes four to six hours to recharge.

THE OUTWARDLY SIMILAR VS Supercharged is more fun, because it has two speeds. With the safety-catch off, the right-hand trigger sets it going while the left side controls the fast or slow options. This means you can continue to make progress even if holding the DPV only with the right hand, although steering in a straight line can be problematic that way.
Its a hundred pounds more expensive than the GTI, but it also goes appreciably faster. It weighs around the same but has a shorter run-time of 90 minutes at full speed, which makes sense as it has the same battery. We saw 0.5m/sec come up on our speedometer, and it really seemed to surge forward when the full-speed setting was used.
We liked this one very much indeed and its tiny frontal area meant that the bigger, more expensive Explorer did not outshine it in terms of performance. We thought it provided a lot of fun for £450.
The Explorer would be considered a serious DPV if it was all-black, but its day-glo orange plastic parts keep its toy-like image intact.
At 14.5kg, it weighs almost twice as much as each of the others, but it is rated to go to 50m, so we consider it appropriate for serious diving.
A strop at the front of the Explorers watertight nose-cone helps when carrying it.
A fully charged battery is good for two hours, and dont forget that with this little beast doing all the work youll consume less gas, so two-hour dives will be possible.
Our underwater speedometer racked up a creditable 0.6m/sec once the unit had accelerated to full speed.
A little LED indicator in the top of the grip flashes green for a fully charged battery, yellow when in normal use, and red if the battery charge is low. A safety catalyser takes care of any battery gases that may be generated.
The manufacturer says that the Explorer has been engineered to withstand the toughest environment, but we noticed that, badly packed in the car, the cowling round the propeller had distorted so that it fouled. We simply straightened it out by hand before we went diving.

BESIDES HAVING THE MODULAR BATTERY-PACK that pulls out for recharging, it also has the electronics that protect it from over-draining the battery; over-current and overheating protection; a big chunky safety-lock; and an audible warning for any chance of a leak.
It is also designed to operate only intermittently if the leak sensor thinks theres an ingress of water. If its too buoyant (as it might have been for us in the sea), four lead weights can be fitted into the base of the handle grips.
The Explorer has sequential switching. The first pull on the right-hand trigger sets it going, a second makes it go faster, and a third gets it to full speed. If you let go of the left-side trigger, it continues to run, but its very hard to stop it arcing to the left so, if you clear your ears with your right hand, you need to be smart about it.
We felt this model had a performance that matched almost any DPV we have tried, though its hard to make direct comparisons unless you do it on the day.
Naturally, a divers configuration makes a lot of difference. My 6ft 2in frame was only about as fast with the Explorer as my 5ft 5in buddys using the VS Supercharged alongside me. The more kit you carry, the slower you go and the less ground you cover.
You also have to be sure to position a DPV such that your body is not subject to its propeller wash. I found that it was best to hold it parallel to my body but closely below me, but after half an hour of continuous use I was noticing the loading on my wrists.
The prop on each DPV is guarded by a cowl and rear grille. I guess it would be simple to fit a lanyard to clip onto and take a lot of the strain.
For a closer look at Sea-Doo Seascooter DPVs, while away some time at Gatwick Airports duty-free shop. Bear in mind that some inland sites ban or limit use of DPVs.

SPECS
PRICE GTI £349; VS £449; Explorer £599
SPEED GTI 0.4m/sec; VS variable max. 0.5m/sec; Explorer 0.6m/sec
RANGE 2hr (VS 1.5hr)
DEPTH RATING 30m (Explorer 50m)
WEIGHT 8.2kg (Explorer 14.5kg)
CONTACT www.alphad.org