I'm afraid I have no idea who the subjects are - the only thing written on the reverse is a pencilled number, "925." The print is small, measuring only 42 x 66.5 mm, and I suspect could have been taken by a family member, although the number might suggest an itinerant photographers mark. Is the young lady the tousle-haired boy's mother? She seems very young, and is possibly an older sister or other relative instead.
The beach is rather steep and very stony. Other people can be seen - although rather indistinctly - in the background, both in the sea, to the right, and further up the beach, to the left. Also right at the left hand edge are the spoked wheel and steps of a bathing machine. Some ropes lying on the gravel - I hesitate to dignify it by calling it sand - are perhaps to pull the bathing machines back up the beach. This, together with the swimming suits and clothing worn suggest to me a date of perhaps the early 1900s. The Wikipedia article on bathing machines suggests that they had largely disappeared from English beaches by 1914.
For more swimsuit delights, head over to Jasia's Creative Gene blog and check out the Carnival.