Fish is a quick and easy way to replenish hit points. Just click on a Pier and select the "Catch" option. Your player will begin catching fish, and stop when you have a full load. You need either a net or a fishing pole depending on what type of fish you are trying to catch.
Before you can eat the fish, you must cook it on a fire. To make a fire, Get Logs and then Use Firepit. Now you can click the Raw Fish in your inventory, and select the Cook option. The fish is now ready to eat.