35. Shipworms
Shipworms may not seem like something you’d consider horrifying, but if you spoke to sailors hundreds of years ago, they might have a different story. The shipworms were well-known during the era of wooden ships, which was at its height for centuries until mankind realized there were several other buoyant materials possible to use.
Shipworms eat through wood, resulting in wooden ships having entire hulls eaten as well as the bottoms of their ships. This is obviously a terrible issue when on the water. They’re not very small like most worms tend to be, they can get pretty sizable, so it’s easy to spot them. There are even giant versions of the species that can get as big as a large tree branch in width. Sadly, by the time people spot them, the shipworms usually have already done some significant damage.