How is shallow water defined in terms of fathoms?

Shallow water is commonly defined as water that is relatively close to the shoreline and typically has a defined depth that can impact naval and oceanographic operations. The standard definition of shallow water is typically recognized as being 100 fathoms or less. This threshold is significant because water depths greater than 100 fathoms are generally considered deep water, where different oceanographic and acoustic phenomena occur.

In terms of practical applications, this definition helps navigate and conduct operations that are sensitive to variations in depth, particularly in relation to acoustic propagation and sonar performance, which can be significantly affected by shallower depths. Given this context, the selection of 100 fathoms aligns with established guidelines and practices in oceanography and the naval field, making it the correct choice.