This plant is growing on the edge and out in my pond. It doesn't look like slender spike rush...

It resembles a type of Watergrass (Luziola). There are a many sub classes, but I would start there and try to find a identification website for your state or region with photos.

Welcome to the club btw, we could always use more folks with interest in the plant-life around our ponds. Let us know if I have sent you down a rabbit hole.