Is it rough? Seasickness, sea by sea

A sea's reputation comes from its shape, not its size. Shallow basins like the North Sea throw up short, steep chop; open water with a long fetch, like the Drake Passage, builds slow ocean swell; and some of the worst water anywhere, the Pentland Firth, is rough because of tide rather than weather. Pick your crossing below for what drives it, which months are worst, and where to sit.

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Before you sailIs the sea rough today? How to checkWhat the wave heights mean, where to find your marine forecast, and this month's rough and calm waters.

Every crossing at a glance

Water	Region	What drives it	Reputation
Bering Sea	Alaska	Aleutian Low storms over a wide deep basin	very high
Drake Passage	Southern Ocean	No land to stop wind, swell or current	very high
Foveaux Strait	Southern New Zealand	Roaring Forties swell over a shallow seaway	very high
Gulf of Penas	Chilean Patagonia	Open Pacific, westerly storms	very high
Hecate Strait	British Columbia	Shallow strait, steep wind waves, southeast gales	very high
Pentland Firth	Northern Scotland	Tidal races, not wind-driven waves	very high
Backstairs Passage	South Australia	Narrow tidal channel, Southern Ocean wind	high
Badung Strait	Bali, Indonesia	Strong tidal flow, monsoon wind and swell	high
Bass Strait	Southern Australia	Ocean swell shortening over a 60 m shelf	high
Bay of Biscay	North-east Atlantic	Atlantic swell over a shoaling shelf	high
Cabot Strait	Atlantic Canada	Atlantic storm track across an open gulf mouth	high
Celtic Sea	Between Ireland, Cornwall and Brittany	Open Atlantic swell over a shelf sea	high
Cook Strait	New Zealand	Wind against a 5-knot tidal stream	high
East China Sea	Southern Japan	Typhoons and fronts over a shallow sea	high
Galápagos Islands	Ecuador	Open-ocean swell, small fast boats	high
German Bight	North Sea coast of Germany	Shallow open bight with tidal channels	high
Great Australian Bight	Southern Australia	Southern Ocean swell with unlimited fetch	high
Gulf of Alaska	North Pacific	Aleutian Low storms, no island shelter	high
Gulf of Lion	Western Mediterranean	Mistral funnelled down the Rhône valley	high
Gulf of Maine	Maine and Nova Scotia	Open Atlantic gulf, winter gales on a long fetch	high
Jeju Strait	South Korea	Winter wind over a strait between two seas	high
Lake Erie	Great Lakes (Ohio and Ontario)	Shallow lake, seas build fast	high
Lake Huron	Great Lakes (Ontario and Michigan)	Open fetch, winds from any quarter	high
Lake Michigan	US Midwest	Long fetch under autumn gales	high
Lake Superior	Great Lakes (Michigan, Minnesota, Wisconsin and Ontario)	Huge fetch over deep water	high
Lombok Strait	Bali and Lombok, Indonesia	Monsoon winds over open Indian Ocean water	high
Mozambique Channel	South-west Indian Ocean	Cyclone corridor feeding the Agulhas Current	high
North Sea	North-west Europe	Shallow basin, short steep wind chop	high
Norwegian Sea	Northern Europe	Ocean swell at unsheltered capes	high
Santa Barbara Channel	Southern California	Afternoon northwest wind along the islands' north shores	high
Sea of Japan	East Asia	Winter monsoon over a long open fetch	high
Sea of the Hebrides	West coast of Scotland	Partly sheltered sea with Atlantic storms in winter	high
South China Sea	Southeast Asia	Northeast monsoon wind over a deep, open sea	high
St George's Channel	Wales and Ireland	Channel linking the Celtic Sea and the Irish Sea	high
Strait of Bonifacio	Corsica and Sardinia	Mistral squeezed through an 11 km gap	high
Strait of Magellan	Southern Chile	Narrows, strong tide and wind	high
Taiwan Strait	Taiwan	Northeast monsoon over a shallow strait	high
Tasman Sea	South-west Pacific	2,000 km of unbroken westerly fetch	high
Tsugaru Strait	Japan	Winter monsoon seas into a 20 km gap	high
Vestfjorden	Northern Norway	Open bight of sea with strong tidal eddies	high
Adriatic Sea	Central Mediterranean	Katabatic bora gusts off the Dinaric Alps	moderate
Aegean Sea	Eastern Mediterranean	Summer meltemi funnelled down the Aegean	moderate
Andaman Sea	Thailand and the Andaman Islands	Monsoon winds over deep open water	moderate
Balearic Sea	Spain	Short fetch, northerly storms and fronts	moderate
Baltic Sea	Northern Europe	Short steep chop, no ocean swell	moderate
Bay of Fundy	New Brunswick and Nova Scotia	Record tides, swell against the ebb at Digby Gut	moderate
Bay of Islands	Northland, New Zealand	Open Pacific at Cape Brett, islands inside	moderate
Bay of Naples	Southern Italy	West-facing bay, autumn and winter storms	moderate
Beagle Channel	Tierra del Fuego (Argentina and Chile)	Narrow channel, strong westerly winds	moderate
Block Island Sound	Rhode Island, Connecticut and New York	Open to the Atlantic, southerly fetch	moderate
Bocaina Strait	Canary Islands	Trade-wind chop in a short, shallow strait	moderate
Caribbean Sea	Caribbean	Trade winds, winter surges and hurricane season	moderate
Cebu Strait	Philippines	Island channel, rougher in monsoons and typhoons	moderate
Chesapeake Bay	Maryland and Virginia	Shallow bay, long fetch, wind against tide	moderate
Coral Sea	South-west Pacific	Trade-wind chop behind a reef screen	moderate
Cozumel Channel	Mexican Caribbean	Strong current, norte winds	moderate
Delaware Bay	New Jersey and Delaware	Open bay, long fetch and strong currents	moderate
English Channel	North-west Europe	Shallow strait, wind against tide	moderate
Firth of Clyde	West of Scotland	Sheltered firth behind the Kintyre Peninsula	moderate
Flores Sea	Eastern Indonesia	Fast currents in the island channels	moderate
Galway Bay	West of Ireland	Atlantic swell entering through the Aran sounds	moderate
Gozo Channel	Malta	Short, shallow channel between two islands	moderate
Gulf of California	Mexico	Long, deep gulf, brief chubasco storms	moderate
Gulf of Finland	Finland and Estonia	Narrow gulf, wind along its axis	moderate
Gulf of Honduras	Honduras, Guatemala and Belize	Trade winds on open water, storms in late summer	moderate
Gulf of Mexico	North America	Winter northers behind cold fronts	moderate
Gulf of Saint-Malo	Between Brittany, Normandy and the Channel Islands	Huge tides and island reefs in the western Channel	moderate
Gulf of Salerno	Amalfi Coast, Italy	Wide open Tyrrhenian mouth, winter storms	moderate
Gulf of Thailand	South-east Asia	Shallow gulf, monsoon wind chop	moderate
Ha Long Bay	Northern Vietnam	Island-shielded bay, storm-season closures	moderate
Hauraki Gulf	New Zealand	Protected gulf, exposed to north winds	moderate
ʻAlalākeiki Channel	Maui, Hawaii	Afternoon trade winds and strong currents	moderate
ʻAuʻau Channel	Maui, Hawaii	Island-sheltered channel with offshore gusts	moderate
Inside Passage	North Pacific	Island shelter, except at its open crossings	moderate
Ionian Sea	Western Greece and southern Italy	Winter southerlies over deep open water	moderate
Irish Sea	British Isles	Wind against strong tidal streams	moderate
Kattegat	Denmark and Sweden	Shallow sea with tiny tides	moderate
Korea Strait	East Asia	Monsoon chop over a shallow shelf	moderate
Ligurian Sea	North-west Italy and Corsica	Mistral and Gulf of Genoa lows over deep water	moderate
Long Island Sound	New York and Connecticut	Sheltered sound, long east-west fetch	moderate
Malta Channel	Central Mediterranean	Open channel exposed to north-westerly gales	moderate
Mediterranean Sea	Mediterranean	Mistral in the west, meltemi in the Aegean	moderate
Milford Sound	Fiordland, New Zealand	Sheltered fiord with an open-sea mouth	moderate
Mona Passage	Caribbean	Tidal current forced over shallow banks	moderate
Monterey Bay	Central California	Winter storms and swell in an open bight	moderate
Moreton Bay	Brisbane, Australia	Shallow bay behind sand islands, wind chop	moderate
Nantucket Sound	Cape Cod, Massachusetts	Winter gales over shoal-filled water	moderate
Northumberland Strait	Prince Edward Island and Nova Scotia	Shallow, exposed strait, autumn depressions	moderate
Pamlico Sound	Outer Banks, North Carolina	Shallow lagoon, short choppy sea in strong wind	moderate
Pearl River Estuary	Southern China	Shallow estuary, monsoon wind and typhoons	moderate
Pillsbury Sound	US Virgin Islands	Trade-wind chop in a small sound	moderate
Port Phillip	Victoria, Australia	Sheltered bay, turbulent tide at the Heads	moderate
Prince William Sound	South-central Alaska	Sheltered fjords, Gulf swell at the entrance	moderate
Resurrection Bay	Southcentral Alaska	Sheltered fjord, open Gulf of Alaska swell beyond	moderate
Río de la Plata	Argentina and Uruguay	Wind along the river's axis over shallow water	moderate
Rottnest Channel	Western Australia	Open-shelf swell, summer sea breeze	moderate
Salish Sea	North Pacific	Mountain-sheltered basins, one strait open to the Pacific	moderate
San Francisco Bay	Northern California	Funneled summer sea breeze and tidal swirls	moderate
San Pedro Channel	Southern California	Open Pacific channel, spring peak	moderate
Saronic Gulf	Athens, Greece	Summer meltemi, partly sheltered by Attica	moderate
Sea of Åland	Sweden and the Åland Islands	Deep basin joined to the open Baltic	moderate
Sea of Marmara	Istanbul, Turkey	Small basin, wind-built waves over long fetches	moderate
Singapore Strait	South-east Asia	Sheltered strait, monsoon wind chop	moderate
Sir Francis Drake Channel	British Virgin Islands	Steady trade winds between islands	moderate
Skagerrak	Scandinavia	North Sea swell funneled into a narrowing strait	moderate
St Lucia Channel	Eastern Caribbean (Martinique and Saint Lucia)	Trade-wind sea in a gap between islands	moderate
Strait of Gibraltar	Spain and Morocco	Wind funneled between two mountain ranges	moderate
Strait of Malacca	Malaysia and Indonesia	Sheltered strait with Sumatra squalls	moderate
Strait of Messina	Sicily and Calabria	Opposed tides drive strong currents through a 3 km gap	moderate
Straits of Florida	Florida and the Bahamas	Gulf Stream current, trade winds, hurricane season	moderate
Straits of Mackinac	Northern Michigan	Irregular currents and autumn gales between two lakes	moderate
Sydney Harbour	New South Wales, Australia	Harbour with an open ocean entrance	moderate
Table Bay	South Africa	Open to the north-west, winter storm waves	moderate
The Minch	North-west Scotland	Atlantic swell down an open northern door	moderate
The Solent	Southern England	Short fetch with fast tidal streams	moderate
Tyrrhenian Sea	Western Italy, Sardinia and Sicily	Winter mistral and libeccio over deep water	moderate
Verde Island Passage	Philippines	Two monsoons and a typhoon season	moderate
Vieques Sound	Puerto Rico	Steady trade winds over a long fetch, shoals in the west	moderate
Vineyard Sound	Cape Cod, Massachusetts	Wind against tidal current at West Chop	moderate
Whitsunday Passage	Queensland, Australia	Wind across the gap to the islands	moderate
Zanzibar Channel	East Africa	Open Indian Ocean channel, monsoon winds	moderate

Reputation summarises what passengers and published marine information commonly report, not a forecast for your sailing.

Three things make water rough

Depth. Shallow water forces a swell to stand up short and steep. It is why the North Sea and the Irish Sea feel choppy and busy rather than grand, and why the Bay of Biscay turns nasty exactly where the ocean floor rises.

Fetch. The distance wind travels over open water before it reaches you. Nothing interrupts the Southern Ocean, so the Drake Passage and the Tasman Sea build long, heavy swell that arrives regardless of local weather.

Wind against tide. When a strong current runs into an opposing wind, waves pile up short and break. This is why the Pentland Firth can be violent on a clear, still day, and why Cook Strait can turn within hours.

Make space for the practical setup

Once the crossing is planned, prepare Dizzout with your headphones from a dry, stationary seat. Keep the phone and case together before travel.

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Frequently asked questions

What is the roughest sea in the world for cruise ships?+

Among waters that passenger ships regularly cross, the Drake Passage has the strongest reputation: there is no landmass at that latitude to slow the Southern Ocean down. The Bay of Biscay and the Tasman Sea are the two most commonly named by cruise passengers in the northern and southern hemispheres respectively. Roughness on any given day depends far more on the weather that week than on the water's reputation.

Does a bigger ship mean less seasickness?+

Generally yes, and stabilisers help a lot on modern cruise ships, but size does not cancel motion: it changes its character. Large ships roll more slowly and gently, which many people tolerate better, while small fast craft produce sharper, higher-frequency motion that others find worse. Where you are on the vessel often matters more than the vessel's size.

Which is rougher, a short crossing or a long one?+

They are uncomfortable in different ways. A short, shallow crossing like Dover-Calais can be sharp and unpleasant but is over inside two hours. A long ocean crossing is usually a gentler, slower motion, but you are exposed to it for a day or more, and there is no option to simply wait it out on deck until it ends.

Should I take medication before a rough crossing?+

That is a question for a pharmacist or doctor, who can account for your health and anything else you take. The one thing worth knowing in advance is timing: most motion-sickness medication is labelled to be taken before you sail rather than after symptoms start, so it is worth deciding before you board.

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Conditions described across this cluster are typical seasonal patterns drawn from published marine and operator information as of July 2026, not forecasts. Route and operator names are trademarks of their respective owners; Dizzout is not affiliated with or endorsed by them. This page is informational and not medical advice.