A robotic submarine is being used to find out what's in the water that flows off the land into the seafood-growing Tasman Bay.
Scientists from the Cawthron Institute are using the $800,000 device to get information about a plume that flows from the Motueka River into the bay.
Marine scientist, Chris Cornelisen, says the 2.7m-long autonomous underwater vehicle will help find out what contamination is in the water, such as from sewage treatment plants or dairy farms, or heavy metals in run-off from roads.