Of Mice and Water

Did the Vic/SA Border track earlier this year and ran into a mouse plague. Now I had previously Sikaflexed the large firewall grommet [thru which we pass so many of our extra cables], as well as any holes I thought might permit entry of water into the cabin. On other trips, having found no problem with river crossings, I assumed it waterproof and therefore mouse proof. Wrong. The day after the mouse infested campsite I discovered mice living in the cabin, and strewth, weren't they hard to get rid of. I sleep in the van and they had no respect for my need of beauty sleep. There were only 3, but they knew how to party, and one of their favourite dance floors was in the ceiling lining. One even assumed the waltz position with me whilst I lay in my sleeping bag.
On my trips I remove the back seats and carry water in a plastic jerrycan. Its in a position where I realise now it has been leaking through the screw cap and depositing water onto the floor felt underlay. I returned from a trip that included river crossings on Friday and commenced removing the vinyl flooring, only to find it very wet throughout the cabin, although I'm yet to remove the piece along the firewall. I've found at least 1 captive nut hole in the floor that communicates directly to the sub-floor, but it's fairly high [above the gearbox from memory] and I don't think much water would have come through there. There are other similar holes in the floor but they appear to enter blind chambers.
My question therefore is, has anyone else had trouble with water from crossings entering the cabin from holes in the floor? It is of course possible the water has come through the door seals, through the [assumed] mouse hole in the firewall, or it may still be as I originally thought that the water came just from the jerrycan. Or it may be a combination of all. Any ideas?

If the water is deep enough and you are in it long enough, it'll definitely come up though the floor moulding around the gear levers - if you figure out a way to seal that up, then I'm all ears too as I've flooded the car twice through there ... and the door seals ... and the barn door seals ... lmao

and when you take your seats out, dont forget the water will come seeping through those bolt holes and if like me you have removed the tie down points in the boot and like me havent plugged up the holes..... well you'll know what happens lol