I have a pair of extra long 24" hemostats that have come in handy .... and have also been know to use regular old kitchen tongs when it's something I don't want to grab bare handed! I've tried a couple of the 'grabbers' but after a couple times in the salt water they won't open and close readily anymore - even when I rinse them off after use!
I had one of those reach extender for the elderly that worked real well for picking up big stuff. The cable that controlled the grabbers eventually rusted and broke though. Now i have the aquatic gardeners which are OK but only good for small stuff.