In which of the following environments do waterborne patrols operate?

Waterborne patrols operate primarily in seas and lakes because these environments provide the necessary liquid medium for vessels to navigate and perform their missions. The nature of waterborne operations involves using boats or other floating platforms to conduct surveillance, transportation, or combat in maritime settings.

In contrast, fields and valleys, mountain terrain, and dense urban areas do not facilitate the use of watercraft in the same way. Fields and valleys typically pertain to land-based operations where mobility is achieved through vehicles or on foot. Mountain terrain presents challenges related to steep gradients and rocky surfaces, making it unsuitable for waterborne patrols. Dense urban areas, while they may include water features, are generally not conducive to traditional waterborne patrols focused on larger bodies of water like oceans or lakes. Thus, the distinction of seas and lakes specifically highlights the appropriate operational environment for waterborne patrols.