They enforce age the adults only area from the time boarding starts. We were trying to enjoy a relaxing lunch in the Quiet Cove area when a very obnoxious father and his family arrived. The CM in the area very quickly and very nicely explained that this was an adults only area and that only guests 18 or over were allowed to stay in the area. It took a lot to move this man along (he screamed quite a bit about how much money he paid for a cruise and his kids could go wherever they wanted). Just as soon as this family moved, another woman with a crying baby settled in the area. Again the CM tried to politely move her along -- she feigned not understanding because she only spoke Spanish. Didn't work well since the cast member explained the rules in Spanish to her. Still took 20 minutes to get her out of the adult only area. The cast member was very apologetic to us -- we explained it wasn't necessary to apologize but we appreciated what he had to go through to keep adult areas kid free. He said they had to start from the get-go because if they let people use the adult pool area at the start, they had a hard time keeping them out later.