Answer:
filamentous algae
According to 2 sources
Spirogyra is a filamentous algae, commonly found in freshwater ditches and ponds. Go through this article for a brief overview about these algae. Spirogyra is also known as pond silk, as its filaments shine like silk due to the presence of mucilage. The outer cell wall has pectin which dissolves continuously, thereby producing the mucilage