A 6 km coastal walk is not a 6 km suburban stroll. Sand and slick rock slow you down — and the tide does not wait for tired legs. Estimate your finish and compare it to high water before you set off.
Rough proportions are fine — they are normalised to 100% automatically.
Set your distance, surface mix and start time, then press Estimate finish time.
Naismith's rule assumes 5 km/h on a good path, plus 30 minutes for every 300 m of climb. On the coast a path is not a path: we multiply the flat walking time by a weighted surface factor — sand slows you by 1.8× and slippery rock by 1.6×, while firm trail stays at 1.0×. So total = (distance ÷ 5) × (sand%×1.8 + rock%×1.6 + trail%×1.0) + (ascent ÷ 300) × 0.5 h. It is a planning estimate, not a guarantee — add time for photos, breaks and tired legs.
We compare your predicted finish time to the next high tide. Treat high water as the moment low-lying paths go underwater. If you would still be out within the hour before high tide, the tool warns you that you may be cut off and tells you the time you must be back by: high tide minus one hour of safety margin.