Sea Legs was created in 1937.
Sea cucumbers don't have any legs at all.
sea horses don't have legs. they only got on tail.
'''''it has no legs'''''
Depending on context, it may mean that you can't balance very well as you have not yet developed "sea legs".
it has 6 legs
No
no
They have legs but they are called flippers.
Sea lampreys do not have legs.
octopus
"Getting your sea legs" means acclimating to life on a ship. "Getting your land legs" is not quite the opposite, as it refers to adjusting your balance and walk to a non-shifting (land) condition after an extended time at sea.