Common sense and good seamanship frame one of the most important aspects of operating a vessel: maintaining a proper lookout. COLREGS Rule 5 says it all in one sentence: “Every vessel shall at all times maintain a proper lookout by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.”

Although experienced captains do it without even thinking about it, maintaining a proper lookout is a big responsibility. It can be thought of as a management philosophy. After all, “proper” and “appropriate” are meant to apply to any and all situations underway. The captain needs to increase or decrease, habitually, what is needed to maintain a proper lookout with changing conditions such as fog, darkness, speed, traffic congestion, a concentrated fishing fleet or trap buoys.

A “proper lookout” is not so much a person as it is an assessment system. It can be the sole operator of the vessel or an additional person’s vigilant eyes and ears. On a clear day with no traffic, it’s easy to assess the surroundings from the helm by sight and hearing, simply by staying alert, looking around the whole horizon and listening. But if fog rolls in or you are crossing heavily trafficked shipping lanes or passing through an active fishing fleet, it’s time to intensify the lookout effort. That’s where the “as well as by all available means” description comes in. Turn on the radar, post an additional person without other duties, or reduce speed.

In the early days, lookouts’ duties were basic: watch out for vessels, lights, shallow water or reefs, buoys, even icebergs. Having a spyglass or binoculars was a bonus.

Today, “all available means” include, but are not limited to, radar, AIS, an automatic radar plotting aid, vessel traffic services, VHF radio and good old reliable binoculars. The captain has to assess the vessel’s needs, make sure everyone tasked with lookout duty has, and knows how to use, the equipment — and knows which information is expected to be delivered to the operator.

The captain needs to assess the abilities of the person looking out as well. Poor eyesight, side effects of seasickness medication or fatigue, glare from the sun or the boat’s own lights, spray, wind, or an obstruction on deck can affect vision. We all know how a cell phone — even with no service — can be distracting. Hearing, too, may be impaired by wind, rigging and engine noise. Or earbuds.

At night, many captains prefer to be called if a lone lookout is unsure about a target. Sometimes a two-person verification is needed on small boats. Deciphering a target can be difficult after dark, especially in a lumpy seaway without radar. If something feels weird in your stomach, it usually is weird. Trust your instincts. It’s better to wake the captain than to be uncertain.

You may be wondering why there are so many radar-assisted collisions. This is where all the experienced mariners scratch their heads and chime in with the same comment: “They need to look out the window!”

Radar is not required on recreational boats, but if a functional radar is aboard, it must be used whenever it could contribute to the quality of the lookout. As with all tools, radar must be used correctly. Keeping visual track of targets goes hand-in-hand with using electronics. A steady bearing and decreasing range mean a collision is imminent. A relative bearing moving aft hints that the target will pass astern, and one with a forward change foretells of a target passing ahead.

An empty radar screen does not always mean your boat is alone. Some small craft, sandbars and ice make very poor radar targets. A weak contact could be lost when the radar operator tweaks the sensitivity to reduce sea-surface clutter, or the radar might be on the wrong range setting. A lookout may observe a radar contact and make an assumption without taking changing conditions into account.

Radar-assisted collisions occur mainly because radar observers do not double-check what they’re seeing on the screen against other information. Distinguishing between assumption and fact makes for accurate decision-making. It’s easy to become overdependent on radar by assuming a machine will do your job for you. Guard against relinquishing the lookout function to electronics alone. Look out the window.

Even though the chosen methods of maintaining a proper lookout are left to each mariner, it’s the captain’s job to make sure each crew member is trained and knows what is expected of him, and that the equipment is in good working order. Constantly appraise the situation and risk of collision, and use all means available on board.

Double-check all those means against one another. Call a shipmate for a second opinion if you are unsure. In the extreme, if you are still unable to acquire the information you need, then reduce speed or stop.

Everyone off-watch down below is counting on you to be vigilant. Collisions are often preventable by maintaining a proper lookout.

This article originally appeared in the August 2018 issue.