In the vast majority of hotels in 2026, you cannot invite outside guests to use the swimming pool unless they are also registered guests of the hotel. Pool facilities are typically sized based on the number of rooms, and allowing non-guests creates overcrowding, liability issues, and "revenue leakage" for the property. Most modern hotels use key-card access or wristbands to enforce these rules. However, some luxury resorts offer a workaround in the form of a "Day Pass" (often sold through platforms like ResortPass), which allows your friends to pay a fee (ranging from $25 to over $100) to use the pool, gym, and spa for the day. If you are caught bringing unauthorized guests into the pool area, you risk being charged an extra-person fee on your room bill or being asked to leave the property. If your friends are just visiting you for a drink or a meal, they are usually welcome in the lobby and restaurants, but the "recreational" amenities like the pool are almost always strictly reserved for paying overnight guests.