Strange strand of white on rock

[Jicklenop]

I woke up today and noticed a strange strand of a white stringy substance at the base of one of my rocks. It looks like it was put there rather meticulously because of the back and forth pattern, so I wanted to check to see what this might be. It seems to he stuck to the rock for the most part except for the ends. Eggs or a pest? Algae?

 

[ISpeakForTheSeas]

Those are Cerith snail eggs.

 

[Jicklenop]

Thanks! I wondered if they might be eggs of some sort.