Green, slimy, beach balls.
This is a photo from Dee Why Beach, on Australia’s East Coast north of Sydney in 2014. Yeah, it’s covered with small green balls.
This is actually a bloom of a unique type of algae called marumo (or marimo depending on who is spelling it). The name was given by a Japanese botanist in the late 1800 s and translates to “bouncy play ball” or something like that. In Iceland they’re referred to as kúluskítur, which I’m told translates to “ball muck”.
The algae is growing on rocks. The algae grows around the rock mostly covering it, and then on occasion the algae/rock will be hit by the right current to knock it loose, sending it rolling around the ocean floor and possibly up onto the coastline.
These algae balls have been seen around the world, but only on rare occasions, sometimes with years in-between sightings.
References: http://www.sciencealert.com.au/news/20142409-26225.html https://au.news.yahoo.com/nsw/a/25061829/ufos-on-sydney-beach/ http://www.smithsonianmag.com/smart-news/thousands-strange-green-balls-appeared-overnight-beach-australia-180952811/?no-ist