Water Torture Kinky Sex

I am a submissive guy who is the sidepiece of a dominant married bisexual guy. He is into a whole bunch of kinky stuff just like I am. After about a year or so into our relationship I suggested some kinky waterplay. The 2 forms of waterplay that are both erotic to us are dunking my head in the tub and waterboarding me. When it comes to the dunking, as soon as my head is underwater, I am completely at his mercy. I can't come back up until he allows me to. The grip he has on the back of my head is so strong that I can't come up for air no matter how much I struggle to do so. Seeing my feet thrashing around on the bathroom floor as I desperately try to come up for air turns him on. He would hold my head underwater with one hand while repeatedly spanking me hard in the ass with his other hand. He would hold me underwater just long enough for me to start panicking and feeling a bit of discomfort without actually getting hurt. Then I'll be allowed to come back up and suck his cock for a bit as I catch some breaths and then it's back under.
Waterboarding is the other form of water play that we do. For those who don't know what waterboarding is, it involves me lying down with a thin cloth covering up my entire face. He would then pour water on that cloth intermittently. Once that cloth becomes very wet, it becomes difficult or even impossible to breathe even though my head isn't underwater. Whenever water is getting poured on that cloth, I experience a drowning sensation even though I'm not actually underwater. It is indeed a very effective simulation of drowning. He would alternate between pouring water on that cloth and then applying pressure on that wet cloth that's covering up my face. Waterboarding is a form of torture that is mainly used to interrogate people for sensitive, personal information so to make it more realistic, we role played as if he was doing it to get me to tell him the pin to my debit card.