Moss no, algae yes. I know of no species of moss that grows under water. I'll let Bill Cody give you an educated guess on what type of algae it is, the pictures are too blurry to identify it.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).