If the hot tub is letting them drop their inhibitions, that's one thing and at least today Bruce can live with it; if it's instilling feelings they don't have outside the hot tub, that's another, far more troubling matter. He wants to be wanted, but not just for his genetic material or for Hulk or because an alien hot tub has flipped the switches on their libidos and Bruce has a lot of pent up libido. Both he and Tony deserve better than that.

He's not really thinking about what he and Tony deserve. He finally gets to smooth his hand down Tony's back until his hand fits perfectly into the curve just above his ass that he'd been admiring before Tony got in the tub.

But that first physical jolt of want that hits him when Tony brings their bodies together pulls at cautions and precautions and habits that even the hot tub and his abbreviated emotional range can't quite nullify.

The very last thing that Tony needs is to be in a hot tub with Bruce and his body fluids. Murder by orgasm isn't something he ever wants to get out the red pen for in order to write it in his ledger.

"Tony." He's not quite getting the effect he's after when he can't quite seem to drag himself away from kissing. "Tony, hold up. We need to..." Stop. They needed to stop.