When I log to my S3 console I am unable to download multiple selected files (the WebUI allows downloads only when one file is selected):
https://console
What I usually do is mount the s3 bucket (with s3fs) in a linux machine and zip the files I need into one, then I just download that file from any pc/browser.
# mount bucket in file system
/usr/bin/s3fs s3-bucket -o use_cache=/tmp -o allow_other -o uid=1000 -o mp_umask=002 -o multireq_max=5 /mnt/local-s3-bucket-mount
# zip files into one
cd /mnt/local-s3-bucket-mount
zip all-processed-files.zip *.jpg