Every 15 minutes the person on watch is supposed to at a minimum scan the horizon looking for anything we might run into. 15 minutes is the chosen interval aboard Syzygy as we believe it balances differing factors such as: how far you can see at night, how generally busy with other vessel traffic the area is, human comfort. We have a wristwatch aboard Syzygy that has an alarm set to ring every 15 minutes. I would wear it around the band of my headlamp so that it was always extremely close to my ear. Just in case I was sleeping or simply had my eyes deeply closed. I would even wear the watch during the day so that if I got busy doing something, when the alarm rang I would be reminded to, at a minimum, look around for other boats, land, check our course, etc.