It's actually a sea strainer. It is a clear plastic bowl assembly with a screen inside it. You can unscrew the bowl with a special plastic wrench from West Marine or you can use a large pair of channel locks like I do;) don't do it in the water!! Dump out the water in the bowl and clean the screen. Make sure you thread the bowl back on correctly and that the rubber 0 ring seals correctly. Check for leaks and tighten when you put it back in the water.