Algae (Latin for “seaweed”) are a very large and diverse group of eukaryotic organisms, ranging from unicellular genera such as Chlorella and the diatoms to multicellular forms such as the giant kelp, a large brown alga that may grow up to 50 meters in length. (Wikipedia)
Such massive blooms require warm ocean temperatures and waters rich in the elements phosphorus and nitrogen, which are found in fertilizers and can be carried to the coasts by water runoff. While the algae aren’t toxic, big blooms can create oxygen-poor “dead zones” in the water and leave an unpleasant odor on beaches.( National Geographic)
Though this looks cool, but the smell when they decay and oxidize may be intolerant.