Hippocamp, or Hippocampus, is a mythological creature shared by Phoenician and Greek mythology which supposedly looks like a seahorse.
In Greek mythology, Hippocamps were the mounts for Poseidon (the god of horses and sea); whereas for the Romans… Neptune (Roman version of Poseidon) was often described to be riding on a sea-chariot pulled by hippocamps.
Hippocamps were often used in the artworks and sculptures in Roman’s fountains and public baths; some of these ancient arts can still be seen in famous tourist sites like the Roman Baths in Bath, UK and the Trevi Fountain in Rome, Italy.
The mythological creature still has its influence in modern days; hippocamps are featured quite often in fantasy story books, including Harry Potter; and also in various fantasy games like Dungeons & Dragons etc.
[more about Hippocamps on Wiki and Theoi]