Nausea Index: sea crossings

The roughest sea crossings, ranked

Every sea and crossing in our guides carries a roughness rating built from its geography, its weather patterns and what passengers consistently report. This table puts all of them in one list, roughest first, with the mechanism that makes each one move.

This cut of the Dizzout Nausea Index ranks 24 sea crossings. 3 entries sit in the top band, rated notorious: Drake Passage, Foveaux Strait and Pentland Firth. Every rating is the one already published in the entry's own Dizzout guide, so a row summarizes a full guide, not a lab test.

Tap a column heading to re-sort, and open any crossing for its full guide: the rough season, the routes that cross it, and what helps once you are on board.

Rank
1	Drake Passage	Southern Ocean	Passage	Notorious 92	No land to stop wind, swell or current
2	Foveaux Strait	Southern New Zealand	Strait	Notorious 92	Roaring Forties swell over a shallow seaway
3	Pentland Firth	Northern Scotland	Firth	Notorious 92	Tidal races, not wind-driven waves
4	Bass Strait	Southern Australia	Strait	Rough 75	Ocean swell shortening over a 60 m shelf
5	Bay of Biscay	North-east Atlantic	Bay	Rough 75	Atlantic swell over a shoaling shelf
6	Cabot Strait	Atlantic Canada	Strait	Rough 75	Atlantic storm track across an open gulf mouth
7	Cook Strait	New Zealand	Strait	Rough 75	Wind against a 5-knot tidal stream
8	Great Australian Bight	Southern Australia	Bight	Rough 75	Southern Ocean swell with unlimited fetch
9	Gulf of Alaska	North Pacific	Gulf	Rough 75	Aleutian Low storms, no island shelter
10	Gulf of Lion	Western Mediterranean	Gulf	Rough 75	Mistral funnelled down the Rhône valley
11	Mozambique Channel	South-west Indian Ocean	Channel	Rough 75	Cyclone corridor feeding the Agulhas Current
12	North Sea	North-west Europe	Sea	Rough 75	Shallow basin, short steep wind chop
13	Sea of Japan	East Asia	Sea	Rough 75	Winter monsoon over a long open fetch
14	Tasman Sea	South-west Pacific	Sea	Rough 75	2,000 km of unbroken westerly fetch
15	Adriatic Sea	Central Mediterranean	Sea	Manageable 50	Katabatic bora gusts off the Dinaric Alps
16	Aegean Sea	Eastern Mediterranean	Sea	Manageable 50	Summer meltemi funnelled down the Aegean
17	Baltic Sea	Northern Europe	Sea	Manageable 50	Short steep chop, no ocean swell
18	English Channel	North-west Europe	Strait	Manageable 50	Shallow strait, wind against tide
19	Irish Sea	British Isles	Sea	Manageable 50	Wind against strong tidal streams
20	Korea Strait	East Asia	Strait	Manageable 50	Monsoon chop over a shallow shelf
21	Mona Passage	Caribbean	Passage	Manageable 50	Tidal current forced over shallow banks
22	Skagerrak	Scandinavia	Strait	Manageable 50	North Sea swell funneled into a narrowing strait
23	Strait of Gibraltar	Spain and Morocco	Strait	Manageable 50	Wind funneled between two mountain ranges
24	The Minch	North-west Scotland	Strait	Manageable 50	Atlantic swell down an open northern door

24 entries. Equal ratings tie on purpose: the guides rate in four bands, and this table does not pretend to more precision than they carry.

How this table is ranked

Each crossing inherits the rating already published in its Dizzout sea guide. A guide rates a crossing in one of four bands, gentle to notorious, from three things we can actually check: the geography that shapes its waves (fetch, shelf depth, tidal flow), operator and route information, and what passengers consistently report. The bands map to fixed scores (gentle 25, manageable 50, rough 75, notorious 92), equal ratings tie, and the way to break a tie is to read the two guides.

Nothing here is a measurement of your sailing day. A notorious strait has flat afternoons and a manageable sea has ugly ones: the rating is about how often each water misbehaves, not a forecast.

The data behind this table

The full Nausea Index: every rated journey on the site in one cross category list.
The World Nausea Map: the same ratings placed where they actually are.
Motion sickness statistics: who gets motion sick, and how often, with sources.

Booked one of these crossings?

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Questions people ask

What is the roughest sea crossing in the world?

Our guides rate 3 entries notorious, the top band: Drake Passage (No land to stop wind, swell or current); Foveaux Strait (Roaring Forties swell over a shallow seaway); Pentland Firth (Tidal races, not wind-driven waves). Equal ratings tie on purpose, and each name links to the full guide behind its rating.

Does a rough crossing always mean you will be seasick?

No. Susceptibility varies a lot between people, and even the notorious crossings have calm days. The rating tells you how often a water misbehaves, so you know how much preparing matters: pick your sailing season with care, book midships, and have a plan for the first rough hour.

When are these crossings at their worst?

Most of them peak in their local storm season, and several are dramatically calmer for months at a time. Each crossing's guide lists its rough months and its calm ones, which is often the difference between an ugly trip and an unremarkable one.

Keep going

Other cuts of the index: bumpiest road trips, biggest cruise ships, worst disney and universal rides.

Updated 2026-09-05. Ratings and figures come from the Dizzout guides linked in each row and change only when a guide changes. This page is educational and is not medical advice.