My sister nearly drowned a couple years back at Croyde beach in north Devon. They were having a beach party and decided it would be a good idea to go swimming, despite the savage rip-tides that exhist there. 
 
Got swept out about a kilometer and after 45mins swimming was completly knckerd and suddenly knew she was going to die so started swallowing water to speed up the process.  
 
she said, you get an overwhelming sence of calm, peace and well-being. 
 
Its only because one of the guys at the party was a competition sea swimmer, who swam out to save her that shes alive.