hag laps / swimming laps

This is a swimming laps which can change the size. When the drowning persons, holding swimming laps, find it is too large, so he can change the swimming ring size to adapt to his chest by a knob inside the swim lap , so that swimming lap can trap them tightly effortlessly, which can avoid people drown due to exhaustion then fell into the water after a long time. In addition, when it is placed, it can also be completely collapsed, to reduce the volume.