These days it can be a headache to find a place to fly a drone, plus there are licenses and just so many hoops you have to jump through. However, while there are a lot of regulations governing the sky, sea going drones are free of paperwork and roadblocks. Yes, there are consumer oriented ROVs on the market already, but they are largely either toys or industrial tools, and I think there is a definitely a niche for a photography/videography focused ROV from DJI.
1. It needs a gimbal stabilized camera with a large sensor. The camera system from the Mavic 2 Pro would be good, though I think a M4/3 camera with a zoom lens would be ideal. Remember that weight and bulk aren't so much of a problem with an ROV as a UAV. The camera module could be located in a bubble on the front of the ROV to allow for maximum field of view.

2. It would need a decent lighting system capable of illuminating a large area. I'm thinking constant video lights that could swivel to follow the direction of the camera.

3. Powerful motors are necessay to provide both speed and stability. The ROV should be capable of speeding through underwater environments to create cinematic drone style shots. For stabilization, the motors would fire to correct for unwanted pitch and roll.

4. A tether is unfortuntaly a necessary part of ROVs, as wireless signals don't travel well through water. This is just as well, as it prevents the ROV from being lost. Most systems seem to have the ROV connected to a base station cable spool which itself connects wirelessly to a remote control. I would suggest using the existing transmission system found in the Mavic 2, and to make it compatible with the Smart Controller.

I really think this could be a major break for DJI that would make the company less vulnerable to fickle politicians and their misunderstanding of UAVS. It is certainly a product that I would buy for sure! What does everyone else think, is this a device you'd be interested in?

Round here the sea is not very clear, so you wouldn't see much.

Great idea