Emily Ratajkowski is sure somethong to look at ... especially in a tiny bikini hanging out on the front of a yacht.

Emily and a couple friends were out on the water Saturday on the Greek Island of Mykonos, and looked like they were having a real good time while catching some rays. The sun was out ... and so were Emily's buns.

She's been vacationing in Greece for several days now -- Gigi Hadid was with her last week -- and obviously ... she's enjoying her stay.