Teti
Cetus or Ceti signified as a large sea monster, fish, or whale in Greek mythology. Cetus was the offspring of the primordial sea deities Phorcys and Ceto.
its called a ceticeti
The only name I can find for the sea serpent is 'Κῆτος' (Cetus), which simply means a whale, large fish, or sea monster. (CHANGED) also called Ceti
medusa
An eel.
The dragons of Greek mythology - giant, serpentine monsters with rows of sharp teeth; called Drakones.
No. Seahorses are real creatures. They are a fish that is closely related to the pipe fish.
Ceti or Cetus
Mermaid.
merman Triton
Well the Hydra is a dragon is some versions and a serpentine creature... I don't know if he counts as a snake though.
According to Wikipedia, it is of the class "Hydrozoa": http://en.wikipedia.org/wiki/Hydra_(genus)