My dear pre-pubescent son takes a bath with me every day. When he is washed clean all over, his penis becomes erect with his foreskin still covering it. Then, when his penis is stimulated with a hypoallergenic lubricant for children, he says, "I have to pee!" and a small amount of clear liquid leaks from the tip of the foreskin 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.