How long does it take for Bart to pass the tunnel under San Francisco Bay?

There is no tunnel under the San Francisco Bay named, "Bart." The Bay Area Rapid Transit (BART) system of rapid public transit in San Francisco, California, and the surrounding area does not use tunnels under the bay. Instead, BART uses the Transbay Tube, which is an underwater railway tube passing under the bay that enables BART to connect the cities of San Francisco and Oakland.