Which type of umbilical is associated with having the layers wound together in a spiral?

The correct choice is spiral-wound umbilical. This type is specifically designed with multiple layers wound together in a helical or spiral configuration. This construction provides several advantages, including enhanced flexibility and reduced drag when the umbilical is used in a diving operation. The spiral design helps in closely packing the layers, allowing for efficient organization of components such as air supply hoses, communication lines, and other critical functions within a compact form.

Spiral-wound umbilicals are often preferred for their ability to withstand the dynamic movements and stresses experienced during diving activities, while also maintaining the integrity and performance of the various lines it contains. This design contrasts with others, which may not provide the same level of protection or flexibility necessary in underwater operations.

The other options refer to different configurations of umbilicals but do not accurately describe the specific spiral-wound characteristic. Paralleled umbilicals, for instance, run straight alongside each other without the twisted or coiled arrangement. Twisted umbilicals imply that the lines are intertwined but not constructed in the same efficient spiral fashion. Layered umbilicals indicate a stacking of components but lack the specific spiral winding that distinguishes the spiral-wound type.