Seawater systems are also referred to as what, besides one-pass systems?

Seawater systems are commonly referred to as open-loop systems because they use natural seawater as a cooling medium without recirculating it. In an open-loop system, seawater is taken from the ocean, used to cool equipment, and then returned directly to the sea after use. This design is efficient for cooling applications because it eliminates the need for extensive treatment of the water and can handle large volumes as needed.

In contrast, closed-loop systems, as indicated in other choices, involve circulating water within a sealed system to transfer heat without discharging any of the working fluid into the environment. Continuous systems and cycle systems also imply a more regulated approach to water use and treatment, which does not align with the characteristics of an open-loop seawater system. Therefore, the term "open-loop" effectively highlights the nature of how seawater is utilized in such systems.