The highest tides in the world are in Canada’s Bay of Fundy, where the difference between high and low water reaches about 17 meters (56 feet) at Burntcoat Head in Nova Scotia. A close rival sits in Ungava Bay in northern Quebec, where tidal ranges of 16.8 meters have been recorded. Beyond Canada, Alaska’s Cook Inlet produces extreme tides over 11 meters (36 feet), making it home to the only two U.S. locations in the global top 50.
Bay of Fundy: The Reigning Champion
The Bay of Fundy, stretching between Nova Scotia and New Brunswick, holds the official record for the world’s highest tides. At Burntcoat Head, the tidal range has been measured at 17.0 ± 0.2 meters, meaning the water level swings roughly the height of a five-story building between low and high tide twice a day. At low tide, the ocean floor is exposed for hundreds of meters, revealing sea caves, rock formations, and tidal pools. Six hours later, the same spots sit under more than 15 meters of water.
The bay’s shape is the key. It narrows and shallows dramatically as it extends inland, forcing an enormous volume of incoming ocean water into a progressively tighter space. But the real amplifier is resonance. The Bay of Fundy and the connected Gulf of Maine form a basin with a natural resonant period of about 13.3 hours. That’s remarkably close to the 12.4-hour cycle of the dominant ocean tide. Just as pushing a child on a swing at the right rhythm makes them go higher, each tidal pulse arrives at nearly the perfect moment to build on the last one, driving water levels far beyond what geography alone would produce.
Ungava Bay: The Overlooked Rival
Leaf Basin in Ungava Bay, on the northern tip of Quebec, produces tides that are statistically indistinguishable from the Bay of Fundy’s. Measurements taken over 311 days of continuous observation recorded a tidal range of 16.8 ± 0.2 meters. Because the error bars overlap with Fundy’s 17.0 ± 0.2 meters, scientists consider Ungava Bay either a very close runner-up or a co-holder of the title.
Ungava Bay gets far less attention because it’s remote, largely uninhabited, and ice-covered for much of the year. There’s no tourist infrastructure, no interpretive centers, and no easy road access. But the physics are similar: a large volume of ocean water from Hudson Strait funnels into a narrowing bay where resonance amplifies the tidal signal. The debate over which location truly holds the record remains unresolved, largely because long-term monitoring in Ungava Bay is difficult to maintain.
Cook Inlet, Alaska
The highest tides in the United States are in Cook Inlet, the long arm of ocean that reaches past Anchorage into south-central Alaska. Tidal heights vary from about 5.5 meters (18 feet) at Kachemak Bay near the inlet’s mouth to 8.8 meters (29 feet) at Anchorage, with extreme tides exceeding 11 meters (36 feet). At Turnagain Arm, a narrow branch of the inlet south of Anchorage, the average tidal range is 30.3 feet, making it the highest in the country.
Of the top 50 highest-tide locations worldwide, only two are in the United States, and both are in Cook Inlet: Sunrise at Turnagain Arm and Anchorage at Knik Arm. The inlet acts like a long funnel, with the incoming tide compressing into narrower and shallower channels. Turnagain Arm also produces a tidal bore, a visible wave that rushes up the arm as the tide comes in, attracting surfers and sightseers along the Seward Highway.
Why Certain Bays Amplify Tides
Open ocean tides are modest, typically rising and falling less than a meter. The dramatic ranges at places like the Bay of Fundy happen because of two reinforcing effects: funneling and resonance.
Funneling is straightforward. When a tidal surge enters a bay that narrows or shallows toward its head, the same volume of water is squeezed into less space, and the water level rises higher. This is why many of the world’s extreme tide locations are at the far ends of long, tapering inlets.
Resonance is the bigger factor. Every enclosed or semi-enclosed body of water has a natural oscillation period, determined by its length and depth. When that period closely matches the roughly 12.4-hour rhythm of the main ocean tide, each incoming pulse reinforces the previous one. The effect compounds over many cycles, producing tidal ranges several times larger than the open-ocean tide that drives them. The Bay of Fundy’s 13.3-hour resonant period is the closest natural match to the tidal cycle of any large bay on Earth, which is why its tides are the most extreme.
Branching channels add further complexity. When a secondary channel connects to a main tidal channel, it can either amplify or reduce the tidal range in the main channel depending on where the branch joins relative to the tidal wavelength. Branches located more than a quarter wavelength from the closed end of the main channel tend to amplify tides, while those closer to the end tend to reduce them.
Tidal Bores at High-Tide Locations
Some of the world’s highest-tide locations also produce tidal bores: visible waves that travel upstream as the tide rushes into a shallow, narrowing river or inlet. About 100 rivers worldwide produce bores, but the most dramatic is on the Qiantang River at Hangzhou in southeastern China. The Qiantang bore can exceed 4 meters in height, stretch 3 kilometers wide, and travel faster than 24 km/h. At certain spots where waves reflect off the banks, they can reach 10 meters. Its roar is audible more than an hour before it arrives.
The UK has a disproportionate share of tidal bores, with about 20 bore-producing rivers including the Severn, Dee, and Mersey. The Severn bore is the largest in the UK, reaching up to 2 meters and drawing crowds of spectators and surfers. In Alaska, Turnagain Arm’s bore is one of the few in North America, though it’s smaller and less predictable than the Qiantang.
When Tides Reach Their Peak
If you want to see the most extreme tides at any of these locations, timing matters. The highest tides occur during spring tides, which happen twice each lunar month around the new moon and full moon. At these times, the sun, moon, and Earth are aligned, and the sun’s gravitational pull adds to the moon’s, producing extra-high highs and extra-low lows.
The moon’s distance from Earth also plays a role. Once a month, at perigee (its closest approach), the moon’s tide-generating force is stronger than average, producing above-normal ranges. About two weeks later, at apogee (its farthest point), tidal ranges shrink. The very highest tides of the year happen when a spring tide coincides with perigee, sometimes called a perigean spring tide. At the Bay of Fundy, these events can push tidal ranges several feet beyond the already impressive average.
Two sets of spring tides and two sets of neap tides (the smaller tides between springs) occur every lunar month, so you don’t have to wait long for a good show. But checking a local tide table for the specific date and time of the highest predicted tide will make the difference between seeing an impressive tide and seeing a record-breaking one.