Some engineering requirements for space are easier, some are harder. The pressures involved in underwater systems are far greater; in space you're either dealin

Some engineering requirements for space are easier, some are harder. The pressures involved in underwater systems are far greater; in space you're either dealing with no pressure at all (robotic drones) or at most 1atm of pressure (human habitat.) Underwater, the pressure increases by 1atm for every 10 meters of depth [1]. At the sea floor you're looking at 20 to 400 atm depending on where you go, and that affects both robotic drones and human habitats. On the flip side, if you're doing underwater drones then they never have to go more than a handful of km away from a surface vessel, so you can stay physically connected to them. That makes power, communication, and retrieval far easier. [1] https://en.wikipedia.org/wiki/Deep_sea#Pressure https://en.wikipedia.org/wiki/Deep_sea#Pressure