A physiology that requires taking lots of liquid with them to survive.

They evolved in the sea. They require taking lots of liquid with them to "breathe", maybe because they need to be continually immersed in it (they breathe through their whole skin?)

Liquid is much heavier than air. "Manned" missions to orbit would be prohibitively difficult and expensive.

A physiology that requires taking lots of liquid with them to survive.

They evolved in the sea. They require taking lots of liquid with them to "breathe", maybe because they need to be continually immersed in it (they breathe through their whole skin?)

Liquid is much heavier than air. Crewed missions to orbit would be prohibitively difficult and expensive.