A kiddie birthday party aboard a boat took a macabre turn yesterday when its pint-sized passengers spotted a corpse floating in the Hudson off Manhattan’s Pier 40.

The shocked parents of birthday girl Chloe Carvajal, 3, told The Post that they had shelled out $1,500 for the round-trip jaunt around the Statue of Liberty for about 40 guests, including at least 15 youngsters.