Hmmmmm... Flexifoil eh? Might have to reconsider buying that Ion2.

So he released the kite ok, but just didnt manage the swim back. Not totally a kite problem is it? Except perhaps that a kite will take you out further than you can swim. Probably got caught in a rip/undertow. Wind blowing offshore maybe ? We need to know. Inquest will reveal everything anyhow. Its understandable, but naive to just leave the public (like me) to speculate.
Maybe its time to sober up about going too far offshore? I never go offshore without my trusty waterski lifejacket. Sure, it adds weight but ...