The bloody swimmers were named for the bloody stench that followed them as they swam through the ocean. Bloody swimmers weren’t what you’d call a shark. They were much different. The smell of blood came from self-inflicted cuts on their tentacles done to attract scavenger prey. We could smell them coming, so they weren’t much of a threat. However, if a surfing dog didn’t heed the drum beat warning, or swam too far past the break? They became lunch.
Cats never worried about the bloody swimmers because they usually traversed the oceans with their friends, the dolphins. Bloody swimmers were afraid of dolphins. You can learn about dolphins here.