No, you are not charged for beer on the beach. That was a fat one from TA.
Beach towels will be in your room when you arrive. They are usually exchanged at the water sports hut for clean ones either in the afternoon or mornings, which ever works out for you.
If you do not turn in your towel on your last day you will be charged a replacement fee when you check out. I don't know the amount. If you turn it in at the water sports hut they will give you a receipt to present at check out. If you forget to turn it in before they close on your last afternoon then take the beach towels with you to turn in when you check out. At least that was the routine in the past. Maybe someone has more recent policy information.
Don't worry, they are not going to nickel and dime you for "extra" stuff.

