Very few have made the list, but here are the qualifiers.
  1. Whales and Dolphins
    Their blowholes give them an advantage. Yeah they may be underwater creatures, but they're still mammals, they totally have the potential to evolve into astronauts in no time.
  2. Brine Shrimp
    If been told they can adapt to any environment imaginable. These little shrimp don't even need space suits for the mission!
  3. Eels
    I could just see them hanging out on Mars, not sure why.
  4. Jellyfish
    Could sting any alien that comes their way.
  5. Starfish
    Some don't belong in the sea, maybe they just want to be up in space with the others.