Below the break: best underwater scooters and sea scooters

Picture a clear bay, a yacht at anchor and a scooter that pulls you along the reef faster than any fin could. Then you aim it down, and the surface closes above you.

Underwater scooters have gone from dive-shop gadget to one of the most popular water toys on yachts. The range now runs from palm-sized snorkelling scooters to sea scooters with more power than a small outboard.

We compared the main brands sold in Europe. These are published figures, not our own tests.

The line-up: sea scooters vs snorkelling scooters

There are two broad types.

• Sea scooters are large and powerful. You hold the handles and ride on or under the surface at speed. SEABOB, iAQUA and SeaNXT sit here.
• Snorkelling and dive scooters are small and light. They pull you along at a gentle pace and travel easily. Sublue and Waydoo's Subnado sit here.

Sources: Club Marine, Marine Industry News, Watercraft Journal, BoatTest, DeeperBlue, Waydoo.

SEABOB: the yacht toy set wave

SEABOB is made by the German company Cayago and is the best-known name in the class. The F5 range runs from 2.5 to 4.5 kW, and Club Marine quotes speeds of around 14 to 20 km/h on the surface and 13 to 20 km/h under water, depending on model and conditions. The battery is a sealed lithium-ion unit (Club Marine).

The F5 SR is the top model, with seven power levels and 745 N of thrust.

iAQUA and SeaNXT: the power crew

iAQUA builds carbon fibre sea scooters and sells them in Europe through a UK base. Its AquaDart Pro 770 Xtreme has over 5.2 kW, reaches 25 km/h from a standstill in under three seconds and limits depth in 5 m steps up to 45 m, where the motor stops (Marine Industry News).

SeaNXT's Elite uses twin 2 kW motors on a 48 V battery, with a top speed of 18 knots and up to 80 minutes in Eco mode or 40 minutes at top speed (Watercraft Journal, BoatTest).

Sublue and Waydoo: the travel quiver

Sublue, a Tianjin-based maker of underwater robots, builds compact scooters for snorkellers and divers. Its Mix Pro is rated at 1.8 m per second under water with 60 minutes of battery, and down to 40 m for advanced divers with the buoyancy tank removed (DeeperBlue).

Waydoo's Subnado range starts with a 1.4 kg Standard model, and the Plus Twin Engine adds 800 W and 9.3 kg of thrust (Waydoo). Waydoo also sells a travel version it describes as airline approved.

Safety: no wipeouts below the surface

• Never dive deeper than your training allows. A scooter can take you deep fast.
• Ascend slowly. Do not ride a scooter straight up from depth.
• Keep clear of swimmers, boats and propellers.
• Follow the maker's charging and transport rules for lithium batteries.

Our verdict: match the scooter to the water

So, which underwater scooter should you buy? For a yacht or a fast session on the surface, a SEABOB or iAQUA. For snorkelling holidays and easy travel, a Sublue or Waydoo Subnado.

Decide how deep and how fast you really want to go, then buy for that, not for the biggest number on the box. Browse every brand in our underwater scooters directory.