A semisubmersible rig under tow should be ballasted down if __________.

Correct Answer: Option D — motion begins to be excessive

Excessive motion during a semisubmersible tow induces severe dynamic stress on structural members and towing gear. Ballasting down increases draft, lowers the center of gravity, and dampens wave response, protecting the vessel's structural integrity per standard Mobile Offshore Drilling Unit (MODU) tow management practices.