The G.O.A.T. is back on a boat … Tom Brady was seen yachting in Europe once more on Thursday — though he appeared to be without his summer boo, Sofia Vergara.

The NFL legend cruised around Saint Tropez waters … and popped his top to make sure he soaked in all the sun he could while on the ride.

Brady — rockin’ nothing but a pair of small grey shorts — dipped in the ocean a few times … and looked as chiseled as ever when he came up for air.

There was no sign of Vergara, however … a bit of a surprise considering how close the two have gotten since they hit Jeff Bezos and Lauren Sanchez Bezos‘s wedding earlier this month.

The hot couple seemed to hang out on a few occasions following the big Venice bash … including once on a superyacht packed with celebrities.

We were told a week ago the duo were not dating — but were in the midst of a summer fling.