Each open diving bell must—

1. (a) Have an upper section that provides an envelope capable of maintaining a bubble of breathing mixture available to a diver standing on the lower section of the platform with his body through the open bottom and his head in the bubble;
2. (b) Have lifting equipment capable of returning the occupied open bell to the dive location;
3. (c) Have an umbilical; and
4. (d) Be—(1) Made of corrosion-resisting material; or
5. (2) Protected against and maintained free from injurious corrosion.