Most probably it were sailors who created the mythos. During the times of the classical antiquity dugongs abounded along the coasts of the Red Sea and the Indian Ocean. Greek, Phoenician and Egyptian seafarers had been able to observe dugongs in Arabian waters. They could not have missed that these were rather lethargic clumsy aquatic animals, harmless vegetarians with a horizontal tail fluke, Several features however distinguish the seacows from the other marine mammals. Their movement through the water is slow with a graceful movement of their tail.
Females have their teats at the front of their chest.
When excited they shed tears. And the way a dugong mother cuddles her suckling baby in her arms surely touched the tough hellenic sailors. Back home the seafarers remembered these features. The mermaid myth was born. We know that fairy tales and sagas wander around the world over the centuries and millenniums, from one culture to the next, under constant transformation.