Final answer:
A tender receiving a 4-Line pull from a diver is using a system of pre-arranged line pull signals to communicate underwater where verbal communication is not feasible.
Step-by-step explanation:
When a tender receives a 4-Line pull from a diver, it is a form of communication used in underwater diving operations. Line pulls are a series of tugs on a rope or line that connect the diver to the tender or surface support. The number and pattern of these pulls correspond to a pre-arranged set of signals that convey messages from the diver to the tender. A 4-Line pull specifically would refer to a certain message according to the standard line pull signals adopted by the diving team. These signals are essential as they are typically used when verbal communication is not possible due to the diving environment.