On any given weekend there in the Summer, there are sometimes 50 - 100 boats in there. They will raft them off 3 - 4 boats deep off the beach plus a ton more anchored off in the middle.
Jamie is right, the weather was un-seasonably warm that day so people were out using their boats for the last time.
Jamie, let me know and I can help you out getting the contact information for "Dog Lady Island" which is the island inside the HotHole. I have a couple of phone numbers you can call. The last that I heard was the land is currently up for sale. It does have a boat launch (small) on it plus a pavilion for live bands. Also, a decent amount of parking. The guy who bought it had hosted some parties back there with live music & beach volleyball, etc... I think the city pretty much shut him down on it so now he's selling it. The only bad thing is possibly the water level... That time of year, it's very shallow back there.
PM me and I'll give you my number.
Later, Mike