Hard to tell from the picture what it might be. Is it an algae bloom? Floating pollen bloom? Some kind of oil slick? Present a problem to what? Some algae blooms can be harmful to your health so you might not want to play in it.
See if neighbors living there a while know what it is or call your local agricultural center or research google images. Have you tried analyzing it for smell, texture, hardness, etc. You just don't want something that is hard enough to damage your impeller or chunky and or sticky enough to clog up your cooling system. Collect some in a glass container and stir it, shake it, feel it, etc. If it sticks to your fingers, or burns them, or bites you, think of something else to do until it goes away.