The act of takin ones own semen and lauching it into another persons face.
Thomas: Hey, i think we should go Sea Gullin'.
Adam: I wish I could but I just wasted my load onto your sisters face.
In British schools, pre-adolence boys masturbate and then ejaculate into their cupped hand and go up to a school friend or teacher and say, "Sea gulling," as they motion their hand to hit their face with the seamen.
Teacher, "When will the sea gullin' stop?! It's been the fifth load today!"