We use the same method when drilling tile for shower hardware.
A wet sponge will be better than a pool of water as you can control flow of water, instant clean up and you can get the water right to the tip of the drill.

Also, we've found sticking some masking tape over the drill site helps the drill bit to bite quicker and get your initial groove started.

I've never drilled glass before, but the practices hold the same for glass