You usually have no immediate hurry to leave the glider. It floats quite well and something very visible that can keep you half dry is not something you should leave if you have not a much better plan.
Of course very much depends on the water temperature, availability of rescue, distance from the shore... etc....
One of my best friends ditched in the lake of Como, he chose to ditch in front of a camping and he was towed to the shore by a boat without even leaving the aircraft
(and with a girl hugged to the glider's tail who swam for the rescue... but that's another story)