DEPTHX

It was designed to autonomously explore and map underwater sinkholes in northern Mexico, as well as collect water and wall core samples.

[2] The vehicle underwent several different design concepts over the next couple of years as engineers at Stone Aerospace explored various options.

It had redundant navigation systems including 54 sonars, an inertial measurement unit, doppler velocity logger, as well as depth gauges and accelerometers.

[1][8] During the DEPTHX 2007 deployment, the vehicle was able to create 3-D maps of four cenotes in Sistema Zacatón in Tamaulipas, Mexico.

The mapping of Cenote Zacatón was particularly notable because its depth was previously unknown, as human divers had not been successful in attempts to reach the bottom.

[9] DEPTHX was the first robotic system of any kind to implement three-dimensional simultaneous localization and mapping (SLAM).