I don't think any seal would stop all the water getting down into the door so there are a couple of things you can do to help.
First don't take the car out in the rain. Not practical for me as it could rain on a wedding day.
Secondly buy an aerosol can of waxoyl and an aerosol can of hammerite underseal paint. Strip the door down by taking everything off it including the glass and then give the inside of the door around the bottom a good wire brushing to clear any rust and old paint off. Vacuum all the dris out and make sure the drain holes (there are two per door) are clear. Spray paint the inside of the door with the underseal and let it dry. Now spray the inside of the door with the Waxoyl.
Finally make sure those drain holes are still clear and check them as a routine at every service.
The worst thing you can do if your car does get wet is lock it away in a garage or put a car cover over the top of a wet car. If you can leave the car outside but under a carport until it dries this is a lot better as the circulating air will dry the inside of the doors and sills for that matter.
When you have the door stripped down also check the inside of the door skin. There is a sound anti drumming pad that is stuck to the inside of the rear door skins just where the chrome window section finishes. Water can run down this chrome section and the water soaks into the sound anti drumming pad. Over time the water held in this pad rusts the door skin from the inside to out. Treat this area as above with the underseal paint and waxoyl. Below is a picture of a door that has been poorly repaired by cutting out the rust and having a square patch welded in but it shows you where to look for the rust on the inside of the door skin. This is not how to repair the damage as this just warps the door skin. The dark area is where the door skin had warped due to the heat of the welded patch.

- DSCF6702.jpg (3.34 MiB) Viewed 2297 times
I don't think any seal would stop all the water getting down into the door so there are a couple of things you can do to help.
First don't take the car out in the rain. Not practical for me as it could rain on a wedding day.
Secondly buy an aerosol can of waxoyl and an aerosol can of hammerite underseal paint. Strip the door down by taking everything off it including the glass and then give the inside of the door around the bottom a good wire brushing to clear any rust and old paint off. Vacuum all the dris out and make sure the drain holes (there are two per door) are clear. Spray paint the inside of the door with the underseal and let it dry. Now spray the inside of the door with the Waxoyl.
Finally make sure those drain holes are still clear and check them as a routine at every service.
The worst thing you can do if your car does get wet is lock it away in a garage or put a car cover over the top of a wet car. If you can leave the car outside but under a carport until it dries this is a lot better as the circulating air will dry the inside of the doors and sills for that matter.
When you have the door stripped down also check the inside of the door skin. There is a sound anti drumming pad that is stuck to the inside of the rear door skins just where the chrome window section finishes. Water can run down this chrome section and the water soaks into the sound anti drumming pad. Over time the water held in this pad rusts the door skin from the inside to out. Treat this area as above with the underseal paint and waxoyl. Below is a picture of a door that has been poorly repaired by cutting out the rust and having a square patch welded in but it shows you where to look for the rust on the inside of the door skin. This is not how to repair the damage as this just warps the door skin. The dark area is where the door skin had warped due to the heat of the welded patch.
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