You can build an fishing boat as low as 20. It is a tiny wooden rowboat. The fishing boat will become bigger as you increase your level. The RS gold ship will also permit you to travel on the port side only (unless you are in possession of weapons implacments). Fly fish or use standard fishing rods. It is also possible to go fishing using this experience. Fishing for food is a possibility when you're out of food. You could also visit the nearest port.
Many people have suggested as well as in other forums the quest will be needed. Here's my pathetic and fabricated quest. My Sailor's Journey: Quest! The difficulty is easy. Length: Medium. Requirements: Food that cheap RuneScape gold is good armor, a fishing rod. You must be able to take on the level 200 Sea Serpent using only range mage, cannons or catapults. You must finish Pirate's Treasure Quest.