Air intakes source Water in Sills?

I aim to rigorously protect my 2003 mgtf against corrosion and know that one area is the sills. Reading around I see that various people have removed their air intakes and gained access / sight into the sills . Some have used this means to Waxoyl them. Now I am aware that the sills can fill with water and I had thought this mainly entered through the area just behind the front wheel arch at the end of the sill where a load of rubbish can build up. Long ago I glued a rubber sheet right across this. BUT I am now wondering – if you can access the sills from the Air intakes , could not a load of water get into the sills the same way? OR am I missing something?
Views most welcome

Hi and welcome to the forum.

The problem isn't water getting in to the sills but water getting trapped in there.

There are a series of holes in the bottom edge of the sill seam, make sure these are clear.

James