We have this clause in our contract:
POOL: The pool is available to suite guests only and has 2 important rules that have SAFETY in common.
Rule 1: Any person under 18 years of age must be actively supervised by their parent - no exception.
Rule 2: Glass objects not allowed within 10 feet of pool. Broken glass can cause severe personal injury and damage to pool itself.
Although we don't have a pool as part of our amenities, we are careful to make sure our house doesn't become a party house.
For that reason, we make special note of the phone number associated with the person renting. If it is our local area code, we know that is is not w a "real" vacationer, but instead someone looking to use our house for a party or to over-use the amenities.
Anyone who is going to "invite friends over" must have friends who are local - which typically means they are planning to use the house for more than just resting and relaxing.
If you have doubts, don't be afraid to ask whether a guest is local, whether they have a vacation or a party planned, etc. Yes, you might lose a rental alont the way, but it's a rental you wouldn't have wanted in the first place.
Put in a call to your friendly insurance agent and discuss if and to what extent you would be liable for "non-resident guests" on your property. It's vital information to have, whether or not you have a swimming pool. Many insurance companies will not cover visitors who are not registered guests.
How you will prevent people from "coming over for a swim" is another matter, and you will need to have some strong wording in your rental contract. Always refer to the insurance coverage - that seems to intimidate the party people.