Within the Deluded Depths section, there is a section where you need to free the souls of three Drowned Sailors. These are the Drowned Sailors that you would need to beat. These guys have two attacks: They can either hold two bombs in their hand or dig underground to attack. Either shoot the bombs to daze him or dodge the underground attack in order to attack him in return. Rinse and repeat. I would recommend attempting this on the first sailor because the other two have other enemies to deal with at the same time.