I'm playing Subnautica, and I was wondering where my Cuddlefish goes when I ask it to stop following me.
They stay around the spot you told them to stop following you. They might swim around a little, though, and they're easy to miss.
This is vaguely written on the Cuddlefish page of the Subnautica Fandom website:
"The Cuddlefish will either follow the player around or stay in one area when told to. The player can tell it to stop/start following them using RMB."