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 black market.
Defeat all enemies on the way to the bar.
Save Makas on the sea.
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 Daidai on the sea.