It's nice having a box big enough to hold all your riding accessories and keeping them dry and clean in the event you need to use any of them. Looks like you found plenty of mud to test it out.
We have one of those Craftsmans small electric power washers. After yesterday I am thinking we need an upgraded model, lolLOL...looks like you're ready for Freewill's firehose treatment!
I mean if it could sustain this much mud AND pressure wash on top - gotta be really good qualityIf you are looking for a good, water tight box look at the Milwaukee Packout box system. There was 2-3 inches of mud after riding yesterday. I hit this thing hard with the pressure washer, mainly to see if it would leak or not. Not a drop of water was on the inside when I got done. Had to strap it in yesterday since the mount hasn't gotten here yet. Being able to take the box out easily made it a lot easier to clean the bed. I will try and follow up once the mount gets here and get in installed. Will probable add their small cooler to go beside it.