@murray: very true, but remember the oceans are MUCH more vast than the board lets on.
oceans are vast, but I wouldn’t think it would matter as much how vast the ocean is but where in the ocean the subs and destroyers are. If they are close enough to shoot at the enemy, they are close enough for sonar.
I’ve seen a search roll used, maybe in aarhe, or somewhere, where you would roll to see if you could find the enemy ships, whether subs or surface within the zone because it’s so vast, and if found, then you could shoot. you could increase it for each sub/destroyer perhaps.