Eliminate coastal ocean Speckle

Hi everyone,

I’m seeking guidance on a matter.

I’m currently processing a Planetscope super dove image using SNAP to detect Sargassum arrival. I’ve applied the NDVI algorithm for this purpose. My aim is to estimate the area covered by Sargassum, which I’ve attempted using the mask area. However, when I try to apply a range to detect Sargassum, the program erroneously identifies some ocean speckles as Sargassum, even though they are water. How can I eliminate these ocean speckles from the image to accurately identify only the Sargassum?