Yes, penile stimulation

With your huge dick already sticking out of the water it is a easy thing to grab the shaft with one hand and the glans in the other. You start pumping the hand around your shaft and gently massage your glans with the other, gently stimulating your dick. After a while you take your pumping hand away from your shaft and let it roam over your body, until you settle it on massaging your breasts.

Taking your time to achieve orgasm you tease yourself all over your body, until you finally settle on stroking your member with both your hands which are inadquate to cover your dick. Feeling your arousal build higher and higher and your balls tighten you stroke more furiously and ready yourself for your orgasm.

Soon you feel your orgasm upon you and you angle yourself and your cock in a way in the water of the tub that you would ejaculate underwater, so you wouldn't have to deal with cleaning your big load. Then your orgasm hits you and your dick unleashes spurt after spurt of semen, only stopping after a dozen spurts. Carefully avoiding the water mixed with sperm you clean your softening dick and get out of the tub. After drying yourself you wrap yourself in the towel and make your way to your own room. Arriving there you realize it has gotten quite late, so you decide against dressing as you usually sleep naked and you just grab a book and lie down in the bed to read a few pages prior to sleeping.