Supermodel Maryna Linchuk -- Fetch My Loyal Boob Holder!

Forget supermodel butt washer ... there's a new best job in the world ... SUPERMODEL BOOB HOLDER.

And just in time too -- Maryna Linchuk nearly suffered a wardrobe emergency on the beach over the weekend in St. Barts ... stripping out of her bikini and into another outfit ... and her loyal boob-covering attendant jumped to the rescue. No nip slips here! Unfortunately.