Still, it's designed for construction works, not just as a camera. From http://www.harkand.com/wp-content/uploads/2015/07/Triton_XLX...
"The XLX is particularly suited for heavy-duty construction support, where remote intervention tasks are required such as positioning of subsea structures, pipeline/umbilical connection, pipeline repair, component change-out, valve operation, fluid injection, debris removal, plus many more. To enhance the capability of the XLX, it may be fitted with purpose built tooling skids weighing up to 3000kg (3 Te.) in air."
If we need just a camera, much smaller body is required.
It's not possible to simply take the toy you linked to and put it in a different body. I assume you want to see under the water -- you need lights. I assume you want it to move -- you need a better engine, propeller, etc. The body needs to be significantly larger and stronger if you don't want it to be crushed like a tin can.
I think we both agree on that.
My point is that they could be made, if the goal is just monitoring. It could even be passive. No engines, no propeller, just a one-time way to throw the water out of the body to go up.
At a minimum, it's just a ball with a few video cameras, and a cavity that will hold the water, when it's going down, and keeps the air when it's going up. Even light is a nice, not must to have, because we're watching for other submersibles, which emit their own lights.
I still agree that it's not simple. I have not used this word in my statements above.