1. Get Fishing Ticket. 2. Go to Fishing Dock. 3. Select a boat, join the boat. (The more people in the boat, the more fish spawn.) 4. Get harpoons from shop at the rear of the boat. 5. Wait for notice about a school of fish appearing. 6. Shoot at fish coming towards the boat from one side. 7. Shoot at fish swimming away from the boat on the other side. 8. ??? 9. Profit!
When I checked out fishing two days ago, it was full of boats. At least 20 people or so were fishing.