if thats the one at like cairnes or something then its because
1 its a five star hotel
2 the ocean is way to dangerous to swim at the beachs there (i have experience) due to crocs and stinger which are massively abundent up north
3 at some beaches its actually illegal to swim at the beach
4 in case of an oil spill which will shut the beach for months(one happened in the last 48 hours)