Charles Hood gives an underwater scooter a whirl 
SeaJet 5000, £599Diver propulsion vehicles (DPVs) have been in vogue ever since Thunderball hit the big screens back in the mid-60s. Traditionally, they were torpedo-shaped, took three men to carry them when out of water, and supported a variety of deadly looking spearguns either side of the hull.
Today, they are still quite popular with deep-wreck and cave divers, who need to cover the furthest amount of distance in the shortest possible time. However, they are also becoming increasingly common with recreational divers. The problem is that most models are still quite heavy. Most manufacturers rely on the use of sealed lead-acid cells, which pile on the weight, making the units only suitable for home waters. But is this all about to change?
The new Seajet 5000 from Bladefish weighs in at just 4.75kg - that's 250g under the measly hand-luggage allowance of the budget airlines! So how does it manage to be so lightweight? Firstly, it is a revolutionary new design. Instead of the traditional torpedo shape - consisting of nose cone, battery compartment and propeller - the Seajet concept is simply to surround the propeller with a super-light plastic case, which also houses the batteries and motor. And the clever part is that instead of using a single large battery pack, it uses several smaller cells that are attached around the circumference of the housing. Furthermore, these cells are high-capacity lithium-ion, giving up to 120 minutes' run time with a claimed speed of more than three miles per hour.
We've been testing a pair for the past few months in a variety of conditions, and we conclude that they are quite effective. The 5000 model is the top of the range and, to be honest, is the only one really
worth considering, as it is the most powerful and is depth-rated to 50m, whereas the others are really aimed at the snorkeller or for shallower diving. To start the DPV, you simply hold onto each handle and presse the two switches. Three speeds can be selected, but I found I needed to go for the fastest one all the time. One slight drawback is that both switches need to be depressed simultaneously, so if you require a hand to clear your ears, for instance, you to have to stop each time. In sea water, it was about a kilogram negative, and when using it with single set while wearing a drysuit, it propels you along at about the same speed as you could fin unaided (less than two miles per hour).
It is highly manoeuvrable, allowing you to make tight turns and whizz along gullies and swim-throughs. Various lights on the top of the DPV inform you of the battery status, which is useful when judging your diving route. As soon as the red LED illuminates, you know that you are down to 60 per cent - time to head back, while still having 20 per cent as a reserve. Charging the unit also features a variety of flashing LEDs that denote the batteries' charge state. An 80 per cent charge takes two hours and a complete charge takes a mere four hours, so one unit could easily be used for two dives a day. The charging connector is a clever through-case design with a waterproof plug that protects the pins, although it is a bit on the fiddly side - also, our retainer cord broke after the second charge and had to be replaced with bungee cord.
After several dives with the Seajet, it started to become part of my normal diving practice and I'll be sad to see it go. One addition that I would like to see is the provision of some kind of mount at the top for attaching, say, a torch or possibly even a camera. As well as being great fun for the sports diver, I could also see the Seajet being extremely useful to disabled divers, especially those who have lost the use of their legs. At just under 600 quid, it's not bad value either, but its greatest attribute is that you could take it away on holiday as carry-on luggage.
DIVE says...
Lightweight and manouevrable
Value 8 Performance 8
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