As an undergrad project this is rather impressive. But those motors do not look very water resistant. We all know that that shape and those blades are not very efficient in the water. And as others mention the RF signal probably cuts out at a few meters (probably worse in salt water).

Definitely impressive as a proof of concept. A lot of the other problems can be solved with iteration. There are some IP67-rated drone motors meant to both fly and run underwater (available from Westmag for example).

There might be less that can be done about the underwater drag, but if it doesn't need to go long distances underwater that's not as much of a problem. For the RF signal, it can either run autonomously underwater, or use a fibre-optic umbilical, or even convert from an umbilical to wireless when it takes to the air.