During a move to a new location, a jack-up drilling unit with personnel on board is towed through a heavy rainstorm. What signal must be sounded by the drilling rig when visibility is restricted?

Correct Answer: Option A — One prolonged and three short blasts

Under COLREG Rule 35(c), a vessel manned and engaged in towing or pushing, when restricted in her ability to maneuver, shall sound one prolonged and three short blasts. A jack-up drilling unit with personnel on board under tow meets this specialized operational criteria in restricted visibility.