Watch to time air supply in aqualung.

用手表来计算氧气瓶中气体的供应量。

It was a perfection of a valve that made the aqualung possible and put man back into the sea with all the freedom of a fish.

是阀的完善使研究水中呼吸器成为可能，并将人类送到海里，使其象鱼一样自由。