Definitely not urinating.

And it doesnt always need to be a direct stimulation of the G-Spot. Although, imo, it does need the G-Spot to be stimulated when just learning, or discovering the ability to squirt.

These contractions, that promote the forceful cums, are from deeper within the body, as you feel your O building, try and resist cumming, then bear down from your abdominal muscles, push out from within the vagina, and use your abdominal muscles to generate the force behind the squirting.

Some are happy with flooding, some find the whole thing gross, although I cant imagine why, Me I love the absolute force that shoots the fluid out, it is a type of high, so girls, practice this, and make someone in your life wet and happy...