Cyanobacteria are great abstract painters. They're best known for the bright turquoise accent colors they use in compositions like this one at B.B. Clarke. They look like specs of paint or bright little plastic fragments floating in the water, but they are really clumps of blue-green algae. They're bad news in a lot of ways, as this CDC site makes clear. Adults usually have the sense to steer clear of them (although boaters are warned to check first before getting into the water to launch their boats) -- but children and pets do not. It goes without saying you need to watch young children near water, but also be sure to keep your dogs away from the water if there is any chance it may harbor blue-green algae.