There is a whole Disney/Pixar movie in here about a young suckerfish who doesn't pay attention to his parents and gets left behind the first time the whale breaches, and then tries to catch up with them, learning from new friends and hitching a ride with a friendly young dolphin along the way.
They might have some benefit to the host, but they also cost them energy in drag.
Remora are very weird fish and I hate catching them. The only fish that are in the same family are Cobia. They look similar and ride along with manta rays and sharks but I’m not sure if they have the sucking power of Remora.
Am I the only one who thinks: little wormriders getting a ride from Shai-Hulud.