Although there are currently not many consumer underwater drones that are actually being shipped to customers, there are quite a few that are in pre-production. One of the latest, the Navatics MITO, is claimed to shoot steadier video than any other.
Like some other underwater drones we've seen, the MITO doesn't have a control/communications cable running all the way from itself to its shore- or boat-located operator. Instead, it has a 50-meter (165-ft) cable running up to a buoy that it tows along on the surface – the drone's maximum dive depth is 40 m (130 ft).
The buoy in turn wirelessly communicates with a handheld RF remote control unit, up to a distance of 500 m (1,640 ft). The user's iOS or Android smartphone is mounted on that remote unit, running an app that allows them to control the drone, and see what its camera is seeing.
Video is recorded onboard at a maximum resolution of 4K/30fps (8-megapixel stills can also be taken), and is streamed to the user at 1080p. If they wish, the operator can also record video/stills on their phone, using the app's color-correction feature to compensate for the bluish cast of images shot at depth. That said, the drone also features two 1,000-lumen LED spotlights, for properly illuminating its subjects.
And yes, the MITO reportedly shoots very steady video. It uses built-in sensors and a four-axis stabilization algorithm to detect changes to its orientation caused by underwater currents/turbulence, then counteracts them by selectively activating its four thrusters (two vertical and two horizontal). Additionally, users can lock the drone to hold a tilt angle of up to +/- 45 degrees while moving forward – this means it can follow along with a moving subject, while looking up or down at it.
One charge of the lithium-polymer battery should be good for two to four hours of use, although an optional extra battery can be swapped in if needed.
If you're interested, the MITO is currently the subject of a Kickstarter campaign. A pledge of US$1,199 will get you one, when and if it reaches production. The planned retail price is $1,999.
You can see the drone in action, along with footage shot by it, in the following video.
Sources: Kickstarter
