From 15th July 2020 wearing masks is now obligatory:
You have to wear a mask while walking to the beach, or on the beach or if sitting with people other than your household. You do not have to wear a mask while swimming or sunbathing with your own household.
You have to wear a mask while walking around the pool area but not while sunbathing with your household or swimming.
You do not have to wear a mask in your car with people from your own household but if you are taking passengers not in your household you do have to wear a mask.
You do not have to wear a mask while exercising. Walking along the seafront is not exercise.