those bags are called Bambi Buckets. Nowadays the sikorsky skycranes have a hose called a donkey dick that they hover low over water with and suck up to fill their water tanks.
Dangerous for the ground pounders, as several thousand pounds of water dropped often knocks the tops out of trees, which is bad news for folks working under the trees.
It used to be a badge of honor to come into fire camp plastered in retardant, as it meant you were at the head of the fire and were in the middle of the hottest action. Now there are 747's that can drop enough retardant to paint about 2000 people, so no longer much of a thing. Although the ammonia in the phoscheck makes hiking fun if you get it down your neck and into your crotch. burns a bit.