I had footwell paddling pool too, passenger side.
But it was due to a poorly fitting window seal. (Bad fitting on corner by door pull, and it was about half inch short of the end by the mirror)
I went to the scrappy and got hold of a pretty clean looking one (?2). And although it was shorter than my one, I spliced the end of the newer one with a stanley knife and added some more from my original one with super glue.
I also bent the Aluminium seat slighty (that the seal sits on) with the palm of my hand so it had a tighter fit to the window.
No more water in there now. But I'm thinking of taking the door card off again soon and painting the inner side of it with UPVC glue, as a sealant as an extra measure.