Bella was on the beach at 9 weeks as I thought it would be a nice clean place to let her off the lead (washed by the tide twice a day). She stuck very close to my ankles and didn't venture any where near the water. If I stopped walking she dug around my feet - trying to bury me?? It took quite a long time to get her into the shallows and she only swam for the first time because she fell in a rock pool! I think she was quite frightened by the noise of the waves and they must look huge when you are puppy size.
Now (7 years) she loves the beach - eating seaweed especially, or 'killing' it. She lies at the edge of the sea or in rock pools when she gets hot and will only swim if it is to fetch her ball. Even then, she is easily spooked by the size of the waves. Not very brave. My other girl, Mabel (nearly 3 years) again loves the beach (especially tasty seaweed) and running through the water after her ball, but she is not a swimmer - yet! We live in Falmouth and dogs are banned from the beach until 1st October. Poor dogs don't understand.
Of course, all dogs are different...... Have lots of fun with your pup on the beach!