Mermaids can pull sims underwater, causing their needs to drop. Most of the time, the sim who got pulled over has enough time to get out of the ocean before they die by drowning.
And you know what is more terrifying than mermaids? That black cloud-mass like thing that pulls sims underwater. If it happens randomly (and this means that a mermaid isn't summoning it), that sim could drown to death. Thanks to this and shark, these have invaded my dreams where as soon as I send my sims swimming in ocean, they'll immediately get surrounded by sharks and will eventually after short time get pulled underwater and die.
Fortunately, the town neighborhood Ohan'ali Town in Sulani is the safest. Your sim will never encounter a shark there. But Mua Pel'am, that's where your sim is in the most danger.
