component is required, and no tape is required to hold the umbilical together. An additional component such as a video cable for a diver's camera, or a hat light cable, can be added by manually wrapping this additional component into the lay of the existing cabled umbilical. When there is risk of the umbilical cable being damaged by scratching on rock, coral or wreckage, the umbilical bundle may be over-braided with a polypropylene braid cover, or a velcro fastened textile cover. The length of the diver's umbilical will depend on the operational parameters. As a general rule a short umbilical is cheaper and more manageable than a longer one, and provided that it is long enough, shorter is generally safer. The standby diver or bellman's umbilical should generally be about 2 m longer than that of the working diver to allow easy access to the diver in an emergency. A common length established by custom and experience is 30 m for a closed bell diver's umbilical, but this may be varied when circumstances require. For surface oriented work it is often necessary to use a longer umbilical. Deployable length may be controlled by tying off the umbilical at the rack to reduce the risk of the diver approaching known hazards too closely. The IMCA specification is 5 m minimum distance from a hazard. The factors that influence length of a surface oriented umbilical include: The distance from the control point to the underwater worksite. The gas endurance expected from the bailout cylinder at the diving depth. This may be calculated on a return speed of 10 m per minute. Storage space available on a wet bell Type of umbilical, bulk and buoyancy characteristics. Current strength and umbilical drag Obstacles and obstructions that may foul the umbilical Diver umbilicals may be negatively buoyant, neutral or positive, depending on the operational requirements. It is a common practice to mark them at length intervals using colour coded tape. Diving bell Both wet bells and closed bells use a bell umbilical to provide surface-supplied gas, electrical power, communications and heating water to the bell and through the bell gas panel to the divers. It may also return reclaimed breathing gas from the divers to the surface gas system. The bell umbilical is generally not intended for lifting the bell. The bell umbilical is connected to through-hull fittings on a closed bell, which are connected