Does this snail come ashore once in seventy years, as Chazal say the חלזון does?

As we discussed earlier on page 39, it is clear from the Gemara that the חלזון is possible to trap and retrieve at any time, and not just every 70 years. For this reason there were trappers of חלזון that regularly caught חלזון from the ocean year-round. Hence, when the above Gemara speaks about the חלזון rising to the surface once in 70 years, it is certainly speaking about an unusual event where the חלזון becomes much more easily accessible due to a mass surfacing of the species, and not the standard method of catching it in the ocean.

No species, including Murex snails, has as of yet been observed and recorded to surface en masse once in 70 years (or at any regular interval of years).

(Of note is the fact that the Murex does indeed occcasionally climb out of the water onto the dry land or rocks, as this author has observed. The Murex may remain outside the water for several hours of its own volition. This being the case, it is certainly possible for a mass surfacing to occur with this species. Fish and many other aquatic creatures are incapable of this.)

The Radvaz states that this mass surfacing was a miraculous event that only occurred in the times of the Beis Hamikdash. After the גלות began, the חלזון could only be obtained in its natural habitat – deep in the ocean 181.