Sighting, Drift and Swimming in a Straight Line at Sea

Both approaches to open water navigation for swimmers work. What differs is what they cost you, and the cost is what this sets out.

Why swimmers curve

Most people breathe more to one side, which produces a slight asymmetry in stroke and a consistent turn over distance. In a pool the lane and the black line correct that constantly without you being aware of it at all.

In open water nothing corrects it, so a small bias compounds into a large arc within a few hundred metres. Swimmers regularly find they have swum considerably further than the straight-line distance between two points. Bilateral breathing helps but does not remove the need to look where you are going.

How to sight efficiently

Lift the eyes just clear of the water at the front of the stroke, look, and drop the face back before breathing. Sighting on the same stroke as a breath is more efficient than adding an extra head lift.

Along that stretch of coast, every six to ten strokes is a common interval, and rougher water needs it more often rather than less. Lifting the head high slows you and drops the hips, so a low, brief look is the technique to practise. Practise it in a pool before relying on it in the sea, because it feels awkward the first several times.

Choosing something to sight on

From water level your eye height is very low, so small marks on the beach disappear entirely. Choose something large, high and behind your target, such as a building, a headland or a distinctive tree. Buoys are useful but sit low and vanish in chop, so use them together with a larger backstop mark.

Along that stretch of coast, check that the mark will still be visible if you are looking into low sun, which is common on early swims. Identify the marks from the water before you start rather than assuming they will be obvious once you are in.

Current you cannot feel

A cross-shore current moves you steadily sideways without producing any sensation of movement at all. The only reliable way to notice it is to check your position against two fixed shore marks in line with each other. If the alignment of those marks changes, you are being displaced, and the direction tells you which way.

When the wind turns, correcting early by aiming upstream of your target is far easier than correcting at the end of the swim.

This is exactly the technique that small boat navigators use, and it works just as well at swimmer eye level.

Chop, glare and visibility

Short choppy water blocks the view at the moment you sight, so more frequent, quicker looks work better. Tinted or mirrored goggles help enormously into low sun, and clear lenses are better in dull conditions or at dusk. Fogged goggles are the most common cause of losing a line, so treat them before the swim rather than during it.

Swimming toward the sun makes marks almost invisible, which is a reason to plan the outward leg away from it. A tow float does not slow you meaningfully and makes you visible to boats that will not otherwise see you.

Tides, currents and swell are local knowledge, so ask somebody who swims there.

Sharing the water

Swimmers sit very low and are extremely hard to see from a boat, particularly in chop or low light. Stay out of marked navigation channels, harbour entrances and moorings unless the swim is organised and marshalled. Bright caps, tow floats and swimming in a group all raise visibility substantially.

Along that stretch of coast, where boats are present, swimming parallel to the shore and close in is safer than crossing open water. Local harbour authorities often have rules about swimming areas, and they exist because of specific past incidents.

Side by side

The takeaway

Pick a big mark high on the land, and check two shore objects against each other for drift.

The best hours on any shore are the ones before the car parks fill.