This is an interesting picture, but...although I can see some right angles, they don't seem to be the strength of it. I can't see the picture being weakened if the right angles were curves, or were gone. Nice composition and focus.
Not sure how this picture fits into the Right angle challenge, where a right angle should produce the strength of the image. Nice pic though.... But the total score is lowered because it does not fit the challenge in my opinion.
The greens are beautiful. The bright color of the algae brings the foreground out of the picture. Interesting shadows in the algae. Might look good in b&w too.