What did Apollo 13 link up with in space during the mission?

During the Apollo 13 mission, the spacecraft linked up with the Lunar Module (LM) known as "Aquarius." After an oxygen tank explosion damaged the Service Module, the Lunar Module was used as a lifeboat to provide life support and propulsion for the return journey to Earth. The successful docking and subsequent operation of the LM were critical for the safe return of the astronauts.