Sea monsters sometimes do not leave loot. I pout this down to me not noticing the loot notification but just now I killed a lopter and there was definitely no loot - I made a point of watching out for it because it's the second time it's happened.
It's happened to other sea monsters too.
I have had this experience myself, it happened with a loptar and also small Goldmont Pirate ships as well.
They leave loot, but it`s in the deep. You have to dive to catch it.
They leave loot, but it`s in the deep. You have to dive to catch it.
Having to get off of your boat and dive to get the loot seems like a bad mechanic.