I figured working at a marina would be a good way to learn the industry from the ground up. I'm still not sure if I want to concentrate on sailing or power boats. I just don't know enough yet.
Um, maybe so, maybe no.
The marine industry is pretty diversified. Depending on the marina and your actual job, you may find that it's pretty similar to working at the Exxon station although in a more picturesque setting. But you'll never have to empty a holding tank at an Exxon station.
Smaller marinas may only provide dockage or dockage and fuel. Bigger marinas may expose you to repair services, boat brokerages, etc.