Merchant submarine

A merchant submarine is a type of submarine that's used for transporting goods. It looks like a normal submarine, except it has big containers or cargo holds inside of it, instead of a bunch of weapons like a military submarine. The merchant submarine moves through the water like a regular submarine, but it can also dive much deeper than a regular submarine because the cargo holds are made out of special materials that won't collapse under pressure. Merchant submarines also have thick walls and a special engine that can handle the pressures of deep water. Merchant submarines are used to transport cargo, like car parts and food, from one place to another. Sometimes they go all the way to the bottom of the ocean!