Just as I thought. The ship was attacked by Adult Aquantis and only the gods know how many others of our ships have been attacked by these creatures.
And now, they are blatantly showing themselves on the beach, as if rejoicing over the suffering of our lost brothers. Well, the best relief for suffering is vengeance.
Go to the central area of the beach and kill 12 Adult Aquantis so our dead brothers can meet our gods in peace.
Beware. Those creatures are powerful. You might want to go to the southeast to visit the Pillar of Eternity, before heading to the beach.