First, the beach is one big open space and if you are lucky enough to go to one that isn't crammed full of other holidaymakers (memories of the Norfolk coast in mid-winter when we very definitely were the only ones there spring to mind!) there is lots of space for running, jumping and throwing balls; plus the obligatory digging - trenches and sandcastle building and carrying buckets of sand / water / pebbles. All of these activities will help children develop their gross motor skills which in turn help develop their fine motor skills. Another thing that you can do is write big letters and draw huge pictures in the sand - this is great fun for children who may usually be reluctant writers.
Then of course there are all the different object labels to be learnt - sand, sea, cliff, rockpool, lighthouse, shell, crab, starfish, seaweed , bucket, spade, ice cream - the list is endless! And for older children identifying the different types of creatures in a rock pool - how many different types of crustacean can you find?
Lastly the shells and stones can be used for counting, adding and subtracting, comparing sizes and much more.
Have fun on your trip to the beach and see how much "accidental learning" goes on!