Here is some vintage history that may interest you. As you know, the divers received what is called a 'trittico' - a set of watch, compass and depth gauge. The diver didn't necessarily wear all three at once.
The actual diving was done in pairs where the divers swam one above the other. The top diver had a watch and a compass and was the 'navigator, while the bottom one had a watch and a depth gauge and was the 'controller'. These divers were connected by a cord in order to maintain a close distance. These cords were connected to the divers by means of a leather strap.
In the pics are 2 types of cords , the short one is about 2.5M long and the long one is 5.0M.
Hope you enjoy,,,,
Cheers,
Asi