As the oceans warm, a new species of medusa (jelly fish) invades the northern Pacific ocean.
When the jellies begin hunting humans, Captain Percival Ronald Wilson and his crew are hired to hunt them.
The story begins with the disappearance of boaters off the northern coast of America.
The jellies, being a new predator, eat local fish.
When that supply runs low, they turn to hunting human prey.
Twenty-seven feet long and seven feet in diameter, adult jellies possess six strong arms.