Marine expeditions typically start by scanning the seabed with sonar to look for large anomalies and then use an ROV to confirm the structure with video imagery.
In 2017, NOAA was exploring the Gulf of Mexico and thought they had found a shipwreck. Upon deploying their ROV, they found a large number of washing machines scattered on the seabed floor from a shipping container likely lost during a storm.
Full article at: PetaPixel 01sep26