Pat, the brownish stains are from the backwater freshwater and it stains boats. There is some things that will take it right off. I use a product from Home Depot that is a rust stain remover, I dont know the name but it is a powder that you mix with water, and takes the stain right off. I get it when I cross the state to go to the Bahamas, and go through the Calosahatchee and Lake Okeechobee and St Lucie waterway. It makes a big brown stain on the front of the hull and on the swim platform. And yes, red tide can cause lung and throat irritation. Especially when it is rough and fine spray is in the air when the red tide is bad. When it is calm, it usually isnt bad, except for the rotting fish and smell of algae bloom. If the State didnt dump phosphate sludge at the Piney Point Phosphate plant, just South of Tampa into Tampa Bay, it wouldnt do this in the winter, that is unheard of. It will be a red tide as long as they dump it. Its terrible and it causes a lot of tourists to not come back I am sure.