These are rocks formed in this river, some reaching gigantic sizes. San Juan River located in Sucre State-Venezuela.
The photos were taken during the dry season, so the flow is very low.
It's a rock with a lot of moss, it's actually very green.
"This is my entry for the #monomad challenge" LINK @monochromes/monomad-july-7th-please-read-the-contest-rules-before-submitting-your-publications