Here is the full list of all 10 Heroes of the Seven Seas trophies - there are 5 bronze, 4 silver and 1 gold.
Defeat all enemies on the way to the bar.
Defeat the ghost captain Kristic.
Clear the Prison scene.
Defeat all enemies in Prison scene.
Equip the mermaid Bow gun.
Defeat all enemies in navy post.
Killed by the tornado.
Save Makas on the sea.
Defeat all enemies on the way to black market.
Save Daidai on the sea.