Billy Joel's New Lady A Hull of a Woman

10/30/2010 8:30 AM PDT
Billy Joel rocked the boat with his maybe girlfriend earlier this week -- taking her on a pimp-ass yacht ride down the Hudson River in upstate New York.

According to reports, the mystery woman is an exec at Morgan Stanley in NYC -- so girl obviously has experience hitting the mother lode.

As for the boat -- "Captain Jack" was not at the helm ... we hope.