"Add ocean and beach overlays as though they were ordinary overlays, using hexes xx01 and xx02 as the "1" and "2" hexes. As with cropping, negative numbers and negative letters are legal for offboard placement hexes. Since Beach and Ocean overlays often extend off the edge of a board, you will need to either add space by cropping (see above) or place a blank board under the overlays."
That one didn't work with the way the overlays are located in Hell or High Water.
However, I use the Overlay extension and it worked just fine, all sorted now