Actually, you can use Fuse (eluded to by the answer above).
S3FS-FUSE: This is a free, open-source FUSE plugin and an easy-to-use
utility which supports major Linux distributions & MacOS. S3FS also
takes care of caching files locally to improve performance. This
plugin simply shows the Amazon S3 bucket as a drive on your system.
No you can't.
S3 is an object storage, accessed over HTTP or REST for example. Just as you can't mount an HTTP address as a directory you can't mount a S3 bucket as a directory.
Having said that there are some workarounds that expose S3 as a filesystem - e.g. 's3fs' project. How reliable and stable they are I don't know.