waterpermeable.com
Seems the most likely use of water permeable would be some landscaping product that allows the rain to soak through. Name feels missing the product.
waterpermeablemembrane.com looks available to register. This would be a clue to me that waterpermeable might be a hard sale.
Recent reg.
No 'permeable' prior sales records except for PermeablePavement $26xx which names the product.
Other example would be PermeableDriveway
Feels not a bad hold, but have to assign it $x-xx on multiple clues, Good Luck