How well sealed from water is the Patrol?

I’ve never been through a deep water crossing in our GU III Patrol. But since doing a lot of customising over the last year I've noticed there are a few places where water could get in.

I recall that you can see through the floor where the side floor plastic trim on either side of the front seats connects to the floor.

We spent a few weekends this year in very dusty conditions and noticed a build-up of dust inside the wheel arches at the rear, and wonder that if water could get in there, then it could easily get into the cabin.

We've got a HF radio transceiver sitting low under the passenger front seat and so it worries me that if water comes in we will be in no position to call for help with the HF if we need it.

Against all this, the vehicle seems well pressurised when you close the doors. Am I worrying over nothing, or should I be running sealant all over the car (and if so could someone please advise me of any less obvious places I should be plugging up)?

Any comments appreciated.

PS We have fitted a safari snorkel.