An Icebreaker Ship is a vessel that has been designed to break ice. Specifically so that other vessels have a clear path through icy and frozen waters. This enables trade to keep moving and stops the global supply chain grinding to a halt.

IMO stands for the International Maritime Organization. It was established in 1958 through the United Nations to coordinate international maritime safety and related practices.

 An Inert Gas System is a method used in gas tankers to prevent an explosion in the cargo tanks. This entails replacing the cargo (the gas) as it is pumped out by an inert gas. This is usually the exhaust of the tanker’s engine.

Inland Waters refers to water that is inland - such as streams rivers canals lakes and waterways as well as bays estuaries and inlets.

INMARSAT stands for International Maritime Satellite System. A communications system to enable those onboard a vessel to communicate with the shore or other vessels.

An Intermodal Shipment is a shipment of goods that uses different modes of transport to arrive at its destination. For example goods reach the port via rail are loaded onto a ship and then onto trucks once they've reached their destination port.

 An International Load Line Certificate is a certificate which states that a vessel has been inspected and the appropriate load lines (also called the Plimsoll line) have been marked on the sides. The certificate is issued either by a coast guard or other appropriate authority or a classification society.

An International Waterway is a waterway that flows through two or more nations. These can be anything from interocean and inland rivers and canals to international straits. Vessels including merchant ships and warships have the right to free passage through these waterways providing there is no enforced treaty.

Also referred to as coastwise or coastal service Intracoastal is the term used for a domestic shipping route that runs along a single coastline.