mercow

plural mercows

1. Any of several marine mammals of the order Sirenia, including the manatee and dugong; sea-cow.

   Mercow. The description of pretty mermaids frolicking in the water is so widespread that it was thought there must be a real creature lurking behind the legends.

   2012, QI: quite interesting facts about mythical creatures - Telegraph

   1 more example

   Ma ruffled my crew cut. "If you'd been the lookout, you'd've told them these were sea cows, not mermaids, right?" "Right," I said. "Mercows," said Mr. Drake behind us. "Moo. Glub glub glub. Moo."

   2002, Will Shetterly, Dogland