- Astronomers estimate Titan’s largest sea is 1,000 feet deep. On Saturn's largest moon, Titan, lies Kraken Mare, a sea of liquid methane. Astronomers have estimated that sea to be at least 1,000-feet deep near its center - enough room for a potential robotic submarine to explore. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020je006558 5 comments science