This trophy is called "
Island-Hopper" and it requires the user to travel to each port within the game.
When looking at your World Map, the ports are marked with an anchor icon.
Once the ship has been obtained, you can only sail to five (5) locations until advancing the story further into the Zwaardsrust Region and earning the following trophy:
After earning that trophy, you will have to travel to Puerto Valor to open the Sea Gates, earning you the following trophy:
Once again though, there will still be a few ports locked off because they are surrounded by land. You must continue the story through the next part at the town of Lonalulu.
Upon completion of the Lonalulu story, you will receive 'Lorelei's Harp.' With Lorelei's Harp, you can now use the blue portals in the ocean to travel to the landlocked ports. To find the portals needed to reach the last ports, look at your Nautical Map with the Square Button.
Here's the map for reference. The blue dots with the lines are the portals and where they take you upon use:
NOTE: The portal in the top left is not required. Those two ports can be accessed by sailing through the opening it warps you to.