Water surface searches

A datum marker buoy should be chosen to drift at the same speed as the target to the extent reasonably practicable, and to remain visible and identifiable during the search.

A shallow draft, maneuverable vessel is best suited to this work, which may require tight maneuvers among navigational hazards or debris.

[2] A sector search, also known as a Victor Sierra (VS) by the US and Canadian coast guards is a search pattern suitable for a small object in a well defined location that covers a circular area centred on a reported position using a route made up of straight line segments that efficiently covers a circular area, and is adapted to account for drift.

The pattern is steered relative to the datum marker, and the track over the ground may look considerably different due to superposition of drift.

[2] Also known as Bravo Sierra (BS), the barrier search pattern is used when there are strong currents or drift which are expected to carry the target through a gap between geographically fixed points of reference downstream of the estimated datum.

A constant speed of between 5 and 10 knots is suggested for a search for a person in the water, and leg length is determined by time.

[2] Radar has a large range and can be very effective at detecting objects with a form and material suitable for reflecting radio waves back towards their source.

It is affected by all the factors that affect detection of the target from the search platform, such as the size, colour, and type of the target, sea and atmospheric conditions, spray, glare, and illumination, distractors like flotsam, search platform speed and motion, number and eye-level elevation of spotters, and crew fatigue.

Some overlap reduces the risk of missing the target altogether, but increases the time taken to carry out the search coverage of a given area.