The couple was spotted Monday on a mega yacht -- a multi-level vessel that looks damn expensive -- where they were looking out onto the ocean blue ... or at least Bey was, snapping some pics with a digital camera.

Jay eventually was out there as well -- and he, too, was taking photos -- not too far from their kids, who were enjoying an onboard swim with nannies and staff in tow. When you're this rich and you're cruising on a boat this nice ... that's how ya do childcare.

Take a look at this thing in the wide shots ... it's like a floating palace on water.

Seems like the Carter-Knowles brood is enjoying these final days of summer ... but if we're being honest, they can kinda take a vacation like this anytime they want.

Their trip here is well-deserved. Bey's fresh off a major album drop -- her eighth solo project, "Renaissance" topped the charts and crushed in sales ... despite some early criticism of its dance tracks.

Firmly back on her throne ... Queen Bey apparently needs some R&R. Or, in this case, mega R&R.