BTW you can delete all of the local snapshots at once like this:
#!/bin/zsh -f
tmutil listlocalsnapshots / \
| fgrep -i 'com.apple.TimeMachine' \
| sed 's#.*\.##g' \
| sort -u \
| while read line
do
tmutil deletelocalsnapshots "$line"
done
exit 0
# EOF
I thought there was a way to use something like tmutil deletelocalsnapshots 99999999
but now I can't seem to find any reference to it.