Canada is officially looking for defense manufacturing partners to help it significantly expand its submarine fleet as the country looks to secure future shipping routes.

Canada’s Department of National Defence said it’s in the market for up to 12 submarines, an order that would potentially quadruple the country’s current fleet of four. The ministry said that the current fleet of submersibles is getting outdated and costly to maintain, so it wants new conventionally powered submarines that can travel under the ice.

Download and listen to the audio version below and click here to subscribe to the Today in Manufacturing podcast.