Cars that can drive on the sea floor so I can look at cool octopuses and stuff from the comfort of my own vehicle

You would need super traction to get thru all the fish poop. Might even need a little buoyancy to avoid being immersed by it. You might be able to make one by sealing the passenger/driver compartment a bit better than the Titan, and figuring out how to engineer power/tractor source that could withstand the ultra deadly pressure. Power would likely have to be electric with either batteries or one heck of a robust extension cord.