Examples from the Web for watertight
In his opinion the House could no longer keep itself in a compartment apart—especially as it was not a watertight compartment.
In this locomotive the gear is the same as that of the next illustration, but it is securely boxed in a watertight iron cover.
All drain pipes should be proved to be watertight by plugging up the lower end of the drain pipe and filling it with water.
The roofing paper brought down over this board, and tacked to the under side or edge, makes a watertight joint.Carpentry and Woodwork|Edwin W. Foster
It was perfectly dry, as the cases were watertight; so we made a big haul of most useful supplies.A Soldier's Sketches Under Fire|Harold Harvey