Hippomaritimus

Notes:

 * Found at the Siren Sands beach (H/I-9).
 * Spawns every 70 minutes.
 * Seems to have its own spawn, no PH kills necessary.
 * Seems inmune to Sleep, Sleep II, Bind.
 * Blind, Poison, Bio, Paralyze, Slow works on it.

Historical Background
"Hippo" refers to the Ancient Greek word for "horse", and "maritimus" can mean "of the sea" or "of the coast". Therefore, this monster's name means either "horse of the sea" or "horse of the coast", by interpretation.