[propbeanie]

... if you edited the 6-pixel overlap area in any of the surrounding squares, as well as the one you cannot enter, then you might have a "wall" issue. Have you looked externally from the bridge of your boat when you get to the border of that square? In SH4, if you edit that 6-pixel overlap area in any of the squares and do not match EXACTLY the bordering area of the next square, there will then be a pillar of "dirt" at each corner of the affected area, and usually a "wall" of "earth" between them, sometimes just below the surface of the water, and sometimes going up to the limit of the game's "height" , of roughly 2000 meters. I am 99.9% certain that SH3 does the same. Dependent upon your viewing angle, this "wall of earth" may or may not be visible, because of the sheer change in height associated with it... If you do not "see" anything, change the angle of your view, or use the external camera and move around more. Also, double-check the 6-pixel overlap area of all of the nine squares that border each other there.