There are many pools with hot tubs that do not have lifeguards, but they are gated. The CMs locking the gates around the pools will politely notify all the guests in the pool and hot tub that they are closing and the guests will need to leave. Then they will wait until all the guests are out of the gated area and lock the gate. And it will probably be Disney Security who might be locking the gates. If you choose to ignore their request, they will probably repeat their information and wait for you to leave.