Related Clues:
- A single one of those things you see floating in the pool when you don't clean it
- Seaweed or kelp
- Photosynthesizing aquarium denizen
- Makeup of some blooms
- Lake growth
- Minuscule lake organism
- Lowlifes in the aquatic food chain
- Organisms that cause red tide
- Tiny tank plant
- Green growth on anything underwater
- Bit of pond slime
- Birdbath grunge
- Pool gunk
- A predator nearly pulled up seaweed, etc
- Kelp, for example