If you ask any experienced mariner about who’s in charge of a boat, you’ll likely get the same answer. It’s not the captain — it’s the water!
Large waves cause serious navigation, communication, and safety issues while boating. That’s why it’s crucial to watch the waves and understand how wave height affects your navigation.
Let’s start with the basics: How do you measure wave height? Here’s our simple guide.
We measure wave height as the distance between sea level and the wave’s crest. Calculating this onboard a boat is subjective and sometimes difficult, but several methods will give strong results with practice.
With your boat in the trough of a wave and on a level, even keel, any wave that obscures the horizon is greater than the height of your eye. To gauge its height, you can also compare a wave to the deck edge or a structure, such as the handrail.
Always observe the wave face while bowing into it in the trough on an even keel. This is also the best method for judging the surf.
This technique is most useful when observing wave height from land, but you can apply it while underway.
If you know that the distance from the waterline to the top of a buoy is 13 feet, you can use that information to determine the height of the waves passing it and the wave period.
Using a similar method, you can gain a fair estimate of the seas in which an underway vessel is operating. Observe the freeboard of the vessel and its motions on the water to make your estimation.
Observe waves as they pass a fixed structure — such as a breakwall, jetty, or pier — to make fairly accurate wave height estimates. This method can also help you determine the wave period.
Using a digital finder with a fast update speed can give you a very accurate wave height by comparing the depth in the trough with the depth at the crest on an even keel.
Each of these methods provides accurate and useful wave height measurements, but they require practice and experience.
Fine-tune your sense of wave height by comparing your observations to a local Weather Service buoy report. With enough practice, you’ll be able to measure wave heights simply by looking at the waves themselves.
Practicing onboard a boat is the best way to learn how to measure wave height. You can also learn by doing some good old-fashioned studying. Start a course today.
Ask a question, share an experience, or add a helpful tip related to this article. Comments may appear after review to prevent spam.
Unlock 24/7 access to Navi, an AI instructor trained on MLS course material, so you can ask questions, run practice quizzes, and nail your captain’s exam.
Learn what questions to ask and how to prepare for a captain’s license drug test to ensure you avoid the most common application delays.
Discover the three types of drug tests working captains must submit to even after they’ve met the initial USCG drug testing requirements for their license.
Discover how a retired airline pilot became obsessed with the Great Loop and built a thriving captain training business through Mariners Learning System.
Learn which substances the MMC drug test looks for, plus how masking agents and false positives factor in.
Discover the five most common mistakes mariners make on the captain’s license physical, plus a checklist for how to avoid them.
Discover why so many charter captains run out of money and how to plan every startup cost from your vessel purchase to guest-ready outfitting.
Learn how to build a charter business plan that covers pricing, expenses, and marketing so your captain’s license leads to lasting profit.
Transform how you talk about price with proven anchoring strategies and value-first framing that stops charter guests from shopping around.
Discover how charter captains use hybrid pricing models and seasonal adjustments to increase revenue and simplify bookings for every guest type.
