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.
Try Dizzout free. Free, drug-free, designed to help after symptoms start — through the headphones already in your bag.
Every crossing at a glance
| Water | Region | What drives it | Reputation |
|---|---|---|---|
| Drake Passage | Southern Ocean | No land to stop wind, swell or current | very high |
| Pentland Firth | Northern Scotland | Tidal races, not wind-driven waves | very 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 |
| Cook Strait | New Zealand | Wind against a 5-knot tidal stream | 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 |
| North Sea | North-west Europe | Shallow basin, short steep wind chop | high |
| Tasman Sea | South-west Pacific | 2,000 km of unbroken westerly fetch | high |
| Adriatic Sea | Central Mediterranean | Katabatic bora gusts off the Dinaric Alps | moderate |
| Aegean Sea | Eastern Mediterranean | Summer meltemi funnelled down the Aegean | moderate |
| Baltic Sea | Northern Europe | Short steep chop, no ocean swell | moderate |
| English Channel | North-west Europe | Shallow strait, wind against tide | moderate |
| Irish Sea | British Isles | Wind against strong tidal streams | 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.
Already feeling it out there?
Settle Your Stomach Now
Get low and midships, put your earbuds in, open Dizzout and tap play — drug-free calibrated sound designed to help once symptoms have started. No pills, no drowsiness.
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.
Related
Explore more
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.