A ship able to submerge part of itself to load or discharge cargo that can be floated on or off. Usually semi submersible ships are heavy-duty vessels
Ports and Ships: Port news and Shipping Movements in African and, Glossary of maritime terms, Durban, South Africa 2012. http://ports.co.za/maritime-terms.php, (Mrtm/ Ports and Ships - Brit) {538}