There's no time for swimming, or anything that isn't rigidly planned into your itinerary.
There's barely 20 minutes to get back to your room to change or freshen up before your "formal" dinner with the captain.
This is a very concisely planned out two-day larping adventure, not a leisurely stay at a resort. All families are assigned specific times to do each activity, and when they go down to Batuu, and even "surprise story moments" are scheduled to the minute.
I guess if you really don't want to participate in the activities with your family, you can escape back down to the surface using a shuttle (elevator) and get in your car to head to a local bar. Or just sulk in your room while your family fights Tie Fighters without you?