Spoilerific post.
There are 4, Nautilus, Piranha, Blaster, Dumbo
Nautilus, Piranha and the Blaster are like the enemies you see of them, but they work for you now, and the Dumbo lights up the place around you.
The small Nautilus can be received by defeating Nautilus Prime in home waters.
Piranha can be obtained by defeating Mermog Prime near the Kelp forest.
Blaster can be obtained in the end of the energy temple, by opening up a flower with nature form, getting the pearl and placing it in a slot. Then defeat Blaster Prime.
Dumbo you can get near the Veil, where you have to defeat a mean octopussy.
That would be all, if you want screens, say so.