Raphael was sinking fast his weapons acting like anchors on him, he slowly hit the bottom of the lake. His lungs shirt from the lack of air as, as his fingers fumbled with his weapons belt he already let out a bit of air that was needed. He soon lost all of it, and water filled his lungs another person jumped in undoing the belt and pulling Raph up. 
He wasn't breathing Greg started to CPR trying to get his heart going again trying to get his heart to contract on its own, "come on Raph your stronger than this but no way am I doing the kissing CPR on you." There was to much water in his system, he didn't think anyone would want to lose a great guy if a person cared about him in a way.