submarine ride
when 2 males engage in anal intercourse underwater while the man on top is exposing his dick out of the water, acting as a parascope that would be found on a submarine.
Stevo: "Dude, I got in my pool this morning for a quick swim until I saw my bro's cock sticking above the water, and at that point, I knew he was doing the submarine ride."
Tommy: "Ew man that's fucking gross!!"
Tommy: "Ew man that's fucking gross!!"