Related Clues:

• Bit of scum
• Part of a pond problem
• Aquatic organisms
• Primitive water organism
• Chlorophyll-containing microorganism
• Spirogyra, e.g.
• Lake organism
• Bit of ocean life
• Primitive plant
• Simple aquatic organism
• Birdbath organism
• Fish tank organism
• Kelp, for one
• Rootless water life
• Pool microorganism