Are these Diatoms (Microscope)?

[RevMH]

Hopefully these images are clear enough. I have a brown coating across my sand. I thought it was dinos, but I see none under the microscope with 12 different samples.

What I see are these critters in the attached picures. They are elongated and only move slowly forward and backward. I think they're diatoms, but I was hoping to get other opinions.

Thank you!

 

[Rocks reef]

Those appear to be diatoms. Most are non-motile, however, a few species are able to glide over surfaces.