When I encounter a Drowned with a trident (very rarely), he is repeatedly struck by tridents as I strike him with my ax or sword. I have no trident as yet. I look around to see if other Drowned are doing this and there is no one else there. After he is killed and his trident falls to the ocean floor you can see there all the other tridents that struck him (see photo). This has happened twice in the last week.