First of all you have to look at your by-laws regarding the use of the pool and behaviour on common property and their exact wording. Remebr, your by-laws may be very different from any other schemes or the “model” by-laws. Only your scheme’s by-laws are relevant.
Then you get the support of your committee to start getting this under control and the first part of that would be to sent a notice to everyone in the building saying that there have been complaints, that the behaviour is in breach of by-laws and that this will no longer be tolerated. The by-laws are there for a reason and they must be obeyed.
Your next issue is how to police this and you might have to install CCTV to catch the culprits in the act if the behaviour doesn’t improve.
After that, it’s a question of having a committee meeting at which you agree to issue a Notice To Comply and be prepared to follow that up with fines if the breaches continue.
By the way, there was a story recently about a scheme where they filled in the swimming pool because of issues exactly like this.
In fact, if the committee knows the swimming pool is being used inappropriately or in a dangerous way and it fails to make an effort to remedy this, the scheme could be liable for injuries caused when someone slips and falls on a structure they shouldn’t have been on in the first place.