The Chilazon is Gufo Domeh LeYam according to the Gemara (Menachos 41a):
ת”ר חלזון זהו גופו דומה לים וברייתו דומה לדג ועולה אחד לשבעים שנה ובדמו צובעין תכלת לפיכך דמיו יקרים
The Sages taught: This ḥilazon, which is the source of the sky-blue dye used in ritual fringes, has the following characteristics: Its body resembles the sea, its form resembles that of a fish, it emerges once in seventy years, and with its blood one dyes wool sky-blue for ritual fringes. It is scarce, and therefore it is expensive.
(source: https://www.sefaria.org/Menachot.44a.2?lang=bi&with=all&lang2=en)
The Ibn Ezra comments on Tehillim that a Shablul is also Gufo Dumeh LeYam:
כְּמ֣וֹ שַׁ֭בְּלוּל תֶּ֣מֶס יַהֲלֹ֑ךְ נֵ֥פֶל אֵ֝֗שֶׁת בַּל־חָ֥זוּ שָֽׁמֶשׁ׃
“like a snail that melts away as it moves; like a woman’s stillbirth, may they never see the sun!”
Ibn Ezra:
כמו שבלול – בדברי הקדמונים ז”ל: ברא שבלול והוא כדמות דג במים שימס בהליכתו
“Like a snail” = According to the early authorities Z”L: The creation of a Shablul (snail) is similar to that of a fish in the sea that melts as it goes.
Source: https://www.sefaria.org/Psalms.58.9