Situational adaptation as used in this paper is the process of (a) recognizing that a change in the in-situ sonar environment has occurred that could adversely impact system performance and (b) Providing recommendations for system adaptations tailored to the situation that preclude performance degradation. Many diverse types of potential deleterious changes in the situation (e.g., operational constraints on the platform housing the sonar, sonar system state of calibration and readiness, object to be detected and identified, environmental and acoustic, etc.) must be considered. Only those related to the propagation of high-frequency acoustic energy in an active context are addressed. Consideration is further focused (to fit within the allotted time) to ``first-order situational adaptations,'' such as sonar depth, beam tilt angle, and beam pattern. The impact on detection of these most fundamental of possible situational adaptations can be substantial and will be delineated for a realistic generic high-frequency active sonar system in typical shallow-water environments. Examples will be presented for representative seasonal shallow-water sound-speed profile and boundary conditions comparing the improvements in detection performance with and without the situational adaptations of depth change, beam pattern shape, and tilt.