It's probably not advisable to drink the tap water - bottled water is freely available at the bar of the Marhaba Beach to take up to your room if you're staying AI. I'm pretty sure the pool was chlorine and I didn't see any washing machines etc. However if you wash clothes in your room and hang them on the balcony, they'll dry very quickly.

If you're not AI you can get water cheaply in any of the little shops near the hotel. I don't know the official hotel policy regarding taking in drinks etc. bought outside the hotel but as long as you're discreet it won't be any problem. I must admit I've often drunk the tap water without any problems but you find even the locals are inclined to drink the bottled stuff.