I sent an email to one of the companies that sell floats/weights, etc. I hope they give us an answer. I provided a link so they can read the thread, see the photos and read our many answers.
Still searching...
A long time ago, in addition to rocks/stones, the Conch shell was used to weigh down the nets. If you think of the shape of the Conch shell, which is hollow-ish, yes it would certain keep a net from floating. I saw some references to fish net weights called 'Dog Conch' but my patience wore thin looking at results with actual dogs and dog toys, not fishing-related responses. Maybe someone else will have more luck looking for the man-made version of the Dog Conch fish net weight.
Here is a quote from this link:
http://datab.us/i/Fishing%20ne...
"Despite their ornamental value, dog conches are traditionally used by local fishermen as sinkers for their fishing nets."
