It would be great to see more underwater archaeology, I'm sure there's a lot to find. But due to variations in local conditions it's really tough to systematically investigate: every site has to be treated individually. Plus doing anything underwater becomes at least 10× harder and more expensive. Human scientific divers can only work easily down to about 30m: anything significantly deeper requires commercial diving protocols, submersibles, or ROVs which raise the difficulty and cost even further.