Eeerm...lots of sleepingpills ?
Dunno really, i always brought a ball with me so i could play some footie, if the beach is too crowded you can play in the water. Of course you need a few others to join you, playing alone sucks.
But mostly it's just laying down on your back, getting a tan, what else can you do at a beach ? Are there any beachclubs in that area ?