Anywhos, some time after I found the squirt cannon I used it to shoot a wasp nest off my house. One quick trigger pull released a bolt of water that cut that nest right in half. Unfortunately one of the wasps got its revenge right in the back of my neck because my hair was in that silly 90s undercut hairstyle in a ponytail. I immediately dropped the squirt cannon and ran back into the house! I couldn't turn my head for a week. Dear ol' Dad came back the next day with wasp spray...
You did it the wrong way. My parents faced a similar situation 30 years ago.
After we five (two parents, two sister and myself) returned from holidays,
they found a hornet nest in an old dead tree trunk.
Instead of calling firemen (who needs those pussies, really ?) they did just like you - they attacked it, headon with a fire hose, full pressure.
As you found the hard way, water isn't enough.
All right then,
Phase II. Firemen ? what are you talking about ? Would be too easy.
They instead took some gasoline out of the lawn mower tank and poured it into the dead trunk. And then they lit the bonfire, and WOOOF - trunk, nest and hornets burned to cinder and ash.
Job done.
Fast forward 30 years, to the late 2010's.
My mom (75 years and counting) had noted wasps entering and exiting a little hole in the ground.
We all told my four years old kid "don't go there. It's dangerous". He didn't listened.
I then heard scream and saw my kid running like freakkin' Usain Bolt, chased by very angered wasps. He slammed the kitchen door and hurried inside. He was lucky to only have two bites.
For the next six months, any flying insect was seen as threat.
(and, can you believe that ? he was barely forgetting the incident when some weeks later we travelled 10 000 km to Réunion Island only to find, what ?
another wasp nest right under my stepfather kitchen room... and the poor kid was attacked a second time. I mean, really !)
Meanwhile my mom just shrugged her shoulders, took some gasoline out of the lawn mower tank and... you can see where this is going... poured it into the hole, lit the fire, and fried the wasp nest.
job done !