Mamoura Beach used to be the best many years ago, but now its unfortunately too bad.
The public beach is the worst, and a private one (for the residents of Mamoura) is better but still not good, the beach is not clean, services are not good, people are not respecting anyone, the sea is not bad, but not clean.
There is a part from the beach which is owned by paradise hotel, its much better, and they have a cafe there with a very nice view.
Mamoura itself is nice, but not a must if you are visiting alex for few days, a walk there is nice especially in Spring, Autumn or winter.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.