Marcus's laugh was maybe a bit to high and a bit to shrill, but he laughed all the same as he continued to unevenly tred water.  Over and over again he'd think he had it and could relax but would quickly find himself moving lower and panic, splashing about a bit before steadying out again. It was a vicious cycle but he endured it.  "Is this, is this all there is to swimming?"  He asked, raising his chin in fear of filling his mouth with salt water.