Warm seawater is very corrosive - and it's a scientific fact that doesn't depend on your worldviewCornflakes_91 wrote: ↑Sat Feb 03, 2018 11:04 am"dont ever try to do rocketry better than the russians did since the 60s! its compltely pointless! there can be no improvements!"
That's why Boeing's Starliner spaceship potentially has it easier in the terms of re-usability - because it's designed to soft-land on land, and not splash down. SpaceX, as usual, does it a little bit differently, although it's not entirely their fault - NASA just didn't feel comfortable with fully powered landing. Why did they decide to go all the way back and splash down is beyond me; probably, being short on cash and tech, and not feeling they'd convince NASA that they can do a rocket-assisted landing on land anyway.
Russians actually did land some spacecraft on water - the BOR series of reuseable test vehicles, in the Indian ocean, back in the 70s (and I don't know the reason for that, must check and ask people in the know), but the actual vehicle (that later became the Buran) was of course designed to land on a runway.