The large dock project is a form of transportation carried by semi submersible ship. Semi submersible ship is a special ship specializing in the transportation of super large equipment, also known as semi submersible transport ship and semi submersible mother ship. Its English name is semi submersible ship. It can submerge the loading deck into the water by injecting ballast water, In order to float the super large cargo to be carried (such as large offshore oil drilling platforms, barges, ships and other super long, overweight and indivisible cargo) "into" the loading deck of the semi submersible ship, discharge the ballast water, float the semi submersible ship to fix the cargo, and then transport the cargo to the designated destination. After reaching the destination, the semi submersible will submerge the loading deck into the water again, and the goods carried will "float" out of the loading deck of the semi submersible to complete the unloading and maritime transportation of the goods.