How good an analogy are marine mammals? Whales gestate in water, I’m assuming neutral buoyancy isn’t the same as weightlessness when one gets down to the detail

How good an analogy are marine mammals? Whales gestate in water, I’m assuming neutral buoyancy isn’t the same as weightlessness when one gets down to the details. Perhaps aquatic creatures might adapt better to an extraterrestrial environment: Squids in Space!