“While many people believe that lemmings commit mass suicide when they migrate, this is not the case. Driven by strong biological urges, they will migrate in large groups when population density becomes too great. Lemmings can and do swim and may choose to cross a body of water in search of a new habitat[5]. On occasion, and particularly in the case of the Norway lemmings in Scandinavia, large migrating groups will reach a cliff overlooking the ocean. They will stop until the urge to press on causes them to jump off the cliff and start swimming,”-
“Wave upon wave of demented avengers march cheerfully out of obscurity into the dream.”-
“And Jesus asked him, saying, What is thy name? And he said, Legion: because many devils were entered into him. 31 And they besought him that he would not command them to go out into the deep.(the bottomless pit of space?) 32 And there was there an herd of many swine feeding on the mountain: and they besought him that he would suffer them to enter into them. And he suffered them. 33 Then went the devils out of the man, and entered into the swine: and the herd ran violently down a steep place into the lake,”-
Fish live in practicaly zero gravity and fish are mostly muscle so I think the concern over muscle degeneration in the absence of gravity is not an insurmountable problem.