^^^ what they said.
Disclaimer: Rescuing a detached kite is VERY risky especially if not done properly, especially if it is a large-ish kite (say anything bigger than a 9m). Then again for smaller kites it is generally windier making the kites (yours and the one in the water) more difficult to deal with.
Whatever you do make sure you can quickly ditch the whole lot safely without ending up tangled in kite and or lines.
All this stuff is easier said than done!
Don't touch the bar or the lines. - the biggest danger is the lines and the bar - tension on any of these without the kite being secured could result in the kite powering up and either tearing itself apart or shredding whatever is causing the tension (fingers!). Be aware that the bar and lines might not want to float and so may get caught on whatever is in / under the water. Also if you are in the surf the lines could be anywhere (upwind / downwind).
If the kite is in a stable position the trick is to pick it up on the upwind side (otherwise you will get gift wrapped) but without getting tangled in the lines or bridle. You want to get a hold of the leading edge, closer to the middle of the kite is better, and ideally with the kite on its back is best (less drag). Generally this involves riding close to the kite to see where the lines are, and ride in from the side where there are no lines. Flipping the kite over is tricky and although it makes the drag in easier the flip itself is usually hard.
When riding back in you will need to do it one handed so if you are not confident enough to do that on the day (surf, very windy, small kite etc.) then best to leave the kite alone.
Obviously if the kite is still rolling around don't ride behind (downwind of) it either...
Pulling bridles is not a great idea as they are not much thicker than flying lines.
Attaching yourself to the kite being recovered is also not a great idea in case things go wrong (and they generally do).
Even ditching your kite on to safety and trying to self rescue is tricky as now you have 2 kites to deal with, one without a safety!
Some stable kite positions which work for kite pickups are:
Ideally you want to be carrying the kite like this in your back hand:
Here is another take on things (although I disagree with the pulling on the bridle idea):
www.thekiteboarder.com/2010/06/off-to-the-rescue-advanced-recoveries/
