Chloe and her baby daddy hot felon Jeremy Meeks were cruising on a yacht Friday in Monaco, enjoying the weather, catching a few rays and hugging here and there when she pulled out the pen.

We don't know what she's smoking ... maybe there's no cartridge, but it still raises eyebrows. Doctors have linked marijuana use during pregnancy with increased risk of complications such as low birth weight and premature birth.

There's also a movement afoot promoting edibles for pregnant women to ease nausea.

It has been reported that Jeremy -- who's in the middle of a divorce -- has said he and billionaire Chloe are going to get hitched once his divorce is final.