New York City’s subway system has been steadily replacing its old fleet with newer train models over the past decade. This begs the question of what happens to the old trains once they permanently go out of service. Between 2001 – 2010, the subway reef program offered a solution & a home for the 2,500 retired train cars by introducing them to a new aquatic environment. After their motors, lighting, air conditioning units, etc. were removed, the old subway car shells were placed on the ocean floor. Here they were transformed into artificial subway reefs where they improved the marine environments for a variety of sea life. The new reefs have since attracted sea bass, tuna, mussels, sponges, and coral. Sea Train, a new exhibition at the New York Transit Museum, which opened March 20, features up-close photography of the subway reefs by Stephen Mallon.