Chilazon - A Plant?

The blue-like thread that the Torah tells us to attach to the tziztis is a derivative of the Chilazon snail. The exact definition of the Chilazon as well as the dye it produces was lost to us many years ago. Towards the turn of the nineteenth century, the Radziner Rebbe - R. Gershon Chanoch Heinich Leiner - researched the topic and wrote an entire book on the matter, claiming that he had found the snail. His chassidim wear the dye it produces until today.
R. Yitzchak Halevi Herzog - first chief Rabbi of the State of Israel - wrote his doctorate on the subject and concluded that it was most probably a different fish, but he couldn't conclude for sure on any specific specie. Until today, there is much debate on the subject.
It is interesting to note the Ra'avad's description of the Chilazon:
"...It is impossible to determine if the Chilazon is a fish or a plant. For it is alive and has movement, [yet] it does not move from its place for it is firmly planted in the ground..."
הקדמת הראב"ד לספר יצירה הנתיב השמיני
ועי' בשו"ת נודע ביהודה (תניינא) או"ח סי' ג' ובהערות שם
See here