Have you not heard of learning through play?
It's literally a fundamental part of the curriculum in younger years, and it doesn't mean older kids don't get anything from it.
Playing in the pool - swimming, throwing and catching balls, poolside safety.
Sandcastles - design & tech, science (eg can't build sandcastles with soft dry sand, need damp sand - why?)
The sea - tides, safety around water, rock pooling
Meeting other people from different backgrounds, cultures etc
Different currencies - maths
New foods and drinks
Languages
Learning about self care and relaxing
Aeroplanes - huge science and technology opportunity
Sun safety
Packing for a trip - life skills
These are just the ones off the top of my head.
We go to 'tacky' all inclusive beach and sun holidays because we love them, and my children, aged from teenagers down to 5 all get an incredible amount of learning and enrichment from them, and we live on the coast so go to the beach regularly at home as well.