Wood siding leaks damage.
Superhydrophobic wall siding leaking water.
Then using a drywall saw cut along the line you just scored.
Vinyl siding installs in pieces so gaps and overlaps.
My photo above of ice below some courses of vinyl siding traces a moisture problem traced to improper installation of a through wall vent for a direct vent heating appliance.
If it is a cantilevered area as in this case place your hand at the base of the wall and feel for.
Ultimately water began to appear on the floor of the kitchen inside.
Although vinyl is impervious to water when installed as directed by the manufacturer vinyl siding as a whole is not completely watertight.
Use a utility knife to score a line about 10 inches 25 cm long into your drywall at the location where you see visible signs of a water leak mold discolored drywall etc.
Cut a hole in the wall large enough for your head to fit inside.