Every time someone jumps in the water it instantly spawns 1-4 sharks. Whenever stepping foot on any islands, it instantly spawns skeletons (1-4 groups), phantoms (4-6 of them) and ocean crawlers (3-4 of them). And every time you kill a group it instantly spawns a new group just 1-5 seconds after.
Even came across some new players doing a gold hoarder quest. They were trying to dig for treasure on an island, and they were struggling. When me and my crew met them they had been fighting for 45 minutes unable to dig up anything from the quest they where doing. Me and my crew took care of the enemies so they could dig up their treasure and finish their quest. For new players the game is literally unplayable in its current state.
After the last update on 31st of August the game has gone into hardcore mode regarding the spawn rate of NPC enemies. For new players this means they won't be able to survive out there, other than just staying on their boat and never leave their ship.