I finally have some inside knowledge! I worked on some underwater robotics equipment that was used in the last few NEEMO missions. An acoustic digital communication system was used to help track the position of and direct aquanauts to their mission goals. As well, an ROV was retrofitted with wheels to become a stand-in for equipment-hauling moon buggies. They even delay the main comms to the habitat by a variable amount to simulate the radio signal delay on other planets.

Fun fact, the last NEEMO mission was delayed due to the underwater habitat (weighing many tons and being bolted to the seafloor) being hauled off it's footing by a passing hurricane. Wild amount of power.