It depends on your point of view. Some of the first sea predators were jellyfishes. They were quite the monsters of their time. Even today I wouldn´t like to get stinged by one. Probably giant squid?
oarfish
Probably a sea monster if they are alive
Sea monster background
Chessie, the legendary sea monster, is said to live in the middle of the Chesapeake Bay. Chessie's first reported sighting was in 1943, with the last sighting in 1997.
Lagoona Blue is the Sea Monster girl
no it is not a dragon it is a sea monster
no it is not a dragon it is a sea monster
lagoona
Tiger shark is a sea monster. It starts with the letter T.
On land, the dragon. Sea monster in water.
Cetus is a constellation named after the sea monster from Greek mythology. It represents the sea monster that was sent by Poseidon to devour Andromeda. The name Cetus is Latin for "whale" or "sea monster".
The giant squid has often been called a sea monster.