My dear pre-pubescent son takes a bath with me every day, and when he is washed clean all over, he gets an erection with his foreskin still on. Then, when his penis is stimulated, he says, "I have to pee!" and shoots a small amount of clear liquid from the tip of his penis. Since he is still sexually immature, it should not be semen. And after that, his erect penis does not deflate, so he can repeat it over and over again. He seems pleasant and happy, so we do not consider this to be harmful behavior.