Beware of Mermaids

I can swim through the iciest of waters; The dolphins hunt with me, Then we part ways and feast on our catch; The vision the land dwellers have amuses me, Their picture is hopelessly flawed; We don't have the tail of a fish, Just the ability to swim hard and strong; Our eyes see in the deep dark depths Our voices sing with the waves; The rhythm of the darkness warns the sailors 'Beware of Mermaids'.