From SpongePedia, the First SpongeBob Wiki.
The Trainer is a dark orange fish that trains Larry the Lobster. Not much is known about him, other than the fact that he works at the GYM and is, as his name suggests, a trainer.
He is angry at Larry because he found out in The Krabby Kronicle that he was "beaten up" by Billy.
He is orange and has blue pants. He looks like Frank (Muscular Goldfish) and is not to be confused with the Coach.