Information about Cypraea pyrum and spurca Habitat

[mittelmeer]

Hello,

Im going a bit off topic now, sorry.
A few years ago I found a beached spurca at Corsica. This steered my interest into the cypraea family.
Later in a one week vacation at Sardinia I searched living spurca and lurida by snorkeling.
Unfortunately I was not able to see any Cypraea under rocks in swallow water or hiding in caves.

My questions about lurida and spurca:

1 How rare are they?
2 Do I need to scuba dive?
3 Are there locations where you see them for sure?
4 Do they camouflage/hide that good you can't recognize them easy?
5 Can you find them at crowded and polluted beaches?