AbstractThe untethered remotely operated vehicle (uROV) PICASSO-1, which is controlled in real time from a surface support vessel via a Φ0.9 mm fiber optic cable, is capable of dives to 1,000-m depth at a duration of up to 6 h and yet is deployable from ships of sizes as low as 17 tonnes. The vehicle was developed at the Japan Agency for Marine-Earth Science and Technology, has carried out 63 dives to date, and is now operable by a team of four biologists and one technician. PICASSO-1 can collect video (HDTV × 1, NTSC × 3) and environmental information (depth, temperature, salinity, dissolved oxygen concentration, fluorescence [chlorophyll a proxy], turbidity) concurrently, and this is output with vehicle heading, camera zoom, and other vital statistics via Ethernet. Acoustically obtained vehicle position information, deck and control room video, and sound data streams are also output via Ethernet, and the whole dive is recorded in a synchronous fashion on a logging/playback system that enables dives to be re-enacted in their entirety to facilitate analyses back in the laboratory. Operations have been successfully carried out overseas using a chartered dive boat, and the system represents a leap forward for exploration of the oceans to significant depths but at relatively low cost and with no loss in data quality.