Two options:
1. Enable "show snapshots" on BOTH volume->snapshot configuration and in the Share options
-> Then it should be always visible in the root of the share, and when entering ...\~snapshot in Explorer.
or
2. If you don't want it to always be visible at the root:
Just enable Show Snapshots in the Volume->Snapshot Configuration (not in the Share options)
Now, you need to set a Windows registry key to disable Windows Explorer file/folder caching. That is because the ~snapshot is not presented to Windows when just accessing the share (only when you specifically enter the ~snapshot part).
But because Windows has "all" folders cached, it says "there is no ~snapshot" without even asking Netapp for a new directory listing.
Sorry, right now, I am unable to find the Netapp or Microsoft KB for this... you'll have to search for this yourself ;-(