Some people like to use Restube without a screwed-in CO2 cartridge and go for a swim with the inflated buoy. That is possible, but to protect the inside of the trigger, it makes sense to use the cap if you have screwed out the cartridge.
In recent years, more and more swimmers have started the RESTUBE Safety Partnerships with buoys that have already been inflated. Many also use the inflated buoy for training purposes, as a so-called drag buoy.
The buoy is simply inflated using the mouth valve before going into the water. This increases your visibility for others on the water - such as paddlers, boats or rescue workers. It also saves the weight of the cartridge.