Everyone's heard of coccolithophores, pteropods and euphausids. Old news. Here are some lesser known species floating around in our oceans.
Nurdles for turtles
Japanese dock washes ashore in Oregon
29K rubber duckies' oceanographic odyssey
Funny story behind the pelagic spaghetti worm:
During my semester in Bermuda, my class went on a blue-water dive armed with BCD pockets full of Ziplocks to collect plankton as they drifted by. One of the divers in my class collected this very strange worm. Upon closer inspection, the worm turned out to be a planktonic piece of spaghetti. The rolling swells of the deep water had apparently caused one of the students on the boat to lose his lunch.