Well, Stark has this whole non-magnetic suit thing, and used nanotechnology to take out Emma, which I get. Seems a little too “The Avengers have to win this one,” but it’s plausible. Same with Strange and Magik, since they played it off as Limbo with the home field advantage. Still a little sketchy, but okay.
But yeah, Namor being tag teamed underwater by a guy made of rocks and a normal strong, tough person is just not plausible at all.