Near infrared band in satellites built for cartography have a meaninful result between water and other structures. My guess is results based on the size of the object would be less than meaningful, lots of false positives. Think flocks of white birds or any other surface or near subsurface objects as well as differences in water temperature, shallow water pans, great deal of variability, say mangroves, swamps, wetlands, oceans, ponds, lakes, waves, debris, water plants, animals, subsurface structures, micro islets, subsurface clutter.
Would be hard to pick a true signal from litter unless tuned say, for still deep water. Linear features are easier to extract or general features such as vegetation, points not so much. All depends on how accurate the result you want needs to be.