Do you mean the Fiesta Party Boat or the Playa Mia Beach Break? The boat stops at the beach for a while as part of that tour. It is where the booze flows. If you are strictly going to Playa Mia (aka Playa Sol), there are packages the include an open bar but it has never struck me as being anything close to a drunken party. Actually we have gone to Playa Mia many times and found it to be rather sedate.