Why One Bay Gets 16 m of Tide and a Whole Sea Almost None

At Burntcoat Head, in Canada's Bay of Fundy, the largest tides rise and fall about 16 metres. On most of the Mediterranean coast, the tide is a few tens of centimetres. Same Moon, same Sun, same planet. So why such a difference? With real tide-gauge records, a tide model and depth surveys: the Moon's two bulges (and why that ideal picture isn't the whole story), the points where the tide almost vanishes, why the Gulf of Maine and the Bay of Fundy ring close to the Atlantic's 12 h 25 min beat, and why the Mediterranean, behind the narrow Strait of Gibraltar, responds so little, with two exceptions. Chapters 0:00 Two tides, same Moon 1:07 What pulls the water 3:22 The tide isn't one bulge 4:48 Fundy: a bathtub in time 7:18 The Mediterranean: a sealed room 8:58 Retuning a bay 9:44 Venice: not the tide 10:20 Shape and rhythm Sources and data Burntcoat Head and Saint John water levels (predicted and observed), and tidal datums: Fisheries and Oceans Canada, Canadian Hydrographic Service. Contains information licensed under the Open Government Licence - Canada (https://open.canada.ca/en/open-government-.... Marseille sea level: SHOM / REFMAR, Marseille tide gauge, validated data retrieved 18 Oct 2026, Licence Ouverte / Open Licence 2.0 (Etalab). Eastport, Maine: NOAA CO-OPS (water levels, datums, harmonic constants). Trieste sea level: University of Hawaii Sea Level Center, Fast Delivery data. M2 and S2 tide model: GOT4.10c, R. Ray, NASA Goddard Space Flight Center. Depths: NOAA NCEI ETOPO 2022 Global Relief Model (doi:10.25921/fd45-gt74). Spanish port tidal spans: Puertos del Estado (REDMAR annual reports). Garrett, C. (1972), Tidal resonance in the Bay of Fundy and Gulf of Maine, Nature 238. Desplanque, C. & Mossman, D. J. (2004), Tides and their seminal impact on the geology, geography, history and socio-economics of the Bay of Fundy, Atlantic Geology 40. Butikov, E. I. (2002), A dynamical picture of the oceanic tides, American Journal of Physics 70. Arbic, B. K. et al. (2007), On the resonance and influence of the tides in Ungava Bay and Hudson Strait, Geophysical Research Letters 34. Lozano, C. J. & Candela, J. (1995), The M2 tide in the Mediterranean Sea, Oceanologica Acta 18. Tsimplis, M. N., Proctor, R. & Flather, R. A. (1995), A two-dimensional tidal model for the Mediterranean Sea, J. Geophys. Res. 100. Sannino, G. et al. (2009), on the Strait of Gibraltar's exchange and sill (Camarinal Sill, 284 m). Bouzaiene, M. et al. (2025), Ocean Science (tides in the Gulf of Gabes). Lionello, P. et al. (2021), Extreme floods of Venice, Natural Hazards and Earth System Sciences 21. AVISO (CNES) education pages on tides in the Mediterranean. Fisheries and Oceans Canada (Annapolis Royal tidal station); FORCE (Fundy Ocean Research Centre for Energy). Images The Moon setting over the Earth's limb (iss040e092688), the Bay of Fundy (iss059e059149), the Strait of Gibraltar (iss071e414110) and the Gulf of Gabes (iss071e414023) from the International Space Station; the Earth from Apollo 17 (AS17-148-22727); the Strait of Gibraltar's tide-raised internal waves from the Space Shuttle (STS058-73-009): NASA / JSC. Minas Basin (PIA01912): NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. "Acqua alta a Venezia nel settembre 2009" by JøMa, Public domain, via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Ac...) "Bay of Fundy - Tide Out" by Dylan Kereluk from White Rock, Canada, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0), via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Ba...) "BurntCoat Head Park" by Shawn M. Kent, CC BY 4.0 (https://creativecommons.org/licenses/by/4.0), via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Bu...) "Flower Pot Rocks - The Rocks at Hopewell Cape, New Brunswick (39910431402)" by James Mann from Moncton, New Brunswick, Canada, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0), via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Fl...) "Hall's Harbour harbour" by RobNS, Public domain, via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Ha...) "Hopewell Rocks (7617785390)" by Andrea Schaffer from Sydney, Australia, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0), via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Ho...) "Vieux-Port Marseille" by DanielMichaelPerry, CC0 (http://creativecommons.org/publicdomain/ze..., via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Vi...) All maps and diagrams are drawn by Tide Workings from the data above. Tide Workings is made by OPAF Games.