[mookiemookie]

And while you're hunting those shipping lanes, it's a good idea to submerge periodically and stop your engines to give your hydrophone operator a chance to pick up targets that your watch crew might otherwise miss.

I usually do the dawn and dusk checks when I'm in the open seas, but when I'm patrolling a grid or if I'm in a shipping lane, I submerge at dawn, noon, dusk, and midnight. In poor visibility, I travel submerged and surface to recharge batteries at night. You'll be surprised at how many more targets you find.