It’s getting harder and harder to tell the sea turtles from the straphangers.

Hundreds of abandoned MTA subway cars have been used to form a reef off the South Carolina shoreline — and sea turtles have taken a liking to them.

“They eat on them, sleep on them and even get territorial about their space,” said Bob Martore, artificial-reef manager from South Carolina’s Department of Natural Resources.

Sounds like more than a few subway riders, doesn’t it?

Martore is to discuss subways as artificial reefs tonight at the Upper East Side’s Church of St. Jean Baptiste.