https://kids.guinnessworldrecords.com en

Longest flooded tunnel survey using an ROV

Longest flooded tunnel survey using an ROV
Who
ASI Marine
Where
Finland
When
March 1999
In March 1999, the remotely operated vehicle ASI Mantaro successfully completed a 120km 74.56 miles survey of the Paijanne Tunnel in Finland. Using sonar and video, the robot mapped debris from a collapse in the water-supply tunnel, which was a threat to the drinking water supply to the Helsinki area.