Sea-swimming guide

How do I plan a sea-swim route?

A route is more than a distance. Work out how you will enter, where you can leave, how the tide may move you and what you will do if the plan changes.

Quick answerChoose clear entry and exit points, check the tide and wind for the complete period, and plan a shorter route that keeps an easy exit available. Seyva’s activity window can help you choose when to look more closely; it cannot map every current, obstruction or change in the water.

Choose the exit before the entry

Identify more than one way out, including what the shoreline will look like at the expected finish. Sea walls, groynes, rocks, cliffs, mud and a falling tide can change access after you start.

Allow for movement

Wind and tide can move a swimmer away from the intended line. Headlands, bays, harbour mouths and estuaries may change flow over short distances. Keep the route close enough to the exit you have assessed and avoid relying on a return that requires more effort than the outward leg.

Make the plan easy to change

Agree a turnaround time, tell someone where you are going and carry visible equipment. If the water, visibility or your own condition is different from the plan, shorten the route or leave the water.

Before you go

  • Mark the entry, primary exit and alternative exit before entering.
  • Check wind and tide for the entire route, not only the start time.
  • Look for piers, groynes, boat lanes, rocks, channels and cliffs.
  • Set a turnaround time and tell someone the plan.
  • Keep the route adjustable when the observed conditions change.
Written and reviewed by Ollie BartlettFounder of Seyva and a sea swimmer and paddleboarder based near Worthing. Reviewed 16 September 2026. Seyva is a planning aid, not professional safety advice.