What is the term for a rescue situation involving a victim under an ice sheet?

The correct term for a rescue situation involving a victim under an ice sheet is "sub-ice rescue." This term specifically describes operations conducted beneath an ice surface, where techniques and equipment are tailored for safely locating and retrieving individuals who have fallen through the ice.

"Sub-ice rescue" emphasizes the particular challenges and hazards associated with working in such an environment, including the need for specialized training, gear, and considerations for the safety of both the rescuers and the victim. This is crucial, as dealing with ice presents unique risks compared to other water rescue scenarios.

Other terms like "ice rescue" could be broader and not specifically denote the circumstances of a victim being submerged beneath the ice. Meanwhile, "underwater recovery" usually refers to retrieving objects or people from any underwater situation without specifically implying the presence of ice above. Lastly, "frozen water retrieval" is an ambiguous phrase that does not sufficiently or accurately describe the specific aspects of a rescue occurring under ice. Hence, "sub-ice rescue" accurately encapsulates the rescue context being referred to in the question.