Where is the 15 m mark?

After every start and turn, a swimmer may stay underwater up to 15 metres before their head has to break the surface (freestyle, backstroke and butterfly). To help you spot that line, most lane ropes have a short stretch of differently-colored floats at 15 m. In StrokeLab you simply mark the moment the swimmer's head passes those floats on each length.

Quick rule of thumb: 15 m is three times the backstroke-flag distance. The flags hang 5 m from the wall, so 15 m is a good way down the pool, never the short patch right next to the wall.

Short course 25 yd & 25 m pools

The pool is short, so 15 m lands near the far end of the length, well past halfway (about two-thirds down a 25-yard pool, 60% down a 25 m pool). Look for the colored floats closest to the far wall and time the head as it crosses them.

Short course pool with the 15 m floats highlighted near the far end of the length — Short course — the 15 m floats near the far end

Green marks the color change to time as the swimmer's head passes it. In a short pool this sits close to the far wall, not the wall they pushed off.

Long course 50 m pools

15 m is about one-third of the way down a 50 m pool. Pools differ: some change the rope color just once per end (that's your 15 m mark), while others also color the first 5 m by the wall, so you skip that one and use the next. If a colored patch is right next to the wall, it's the 5 m mark, ignore it.

Long course pool, first colored floats off the wall highlighted as the 15 m mark — Long course — first marker off the wall

Green: here the only color change off the wall is the 15 m line, about a third of the way down. Use it.

Long course pool, first float by the wall crossed out, second color change marked as 15 m — Long course — second marker off the wall

Red by the wall is the 5 m patch, skip it. Green is the next color change: that's your 15 m mark.

Can't see a color change?

Not every pool has 15 m floats. If yours is a single color, estimate it and stay consistent length to length: roughly one-third down a 50 m pool, or about two-thirds down a 25 yd/25 m pool. The backstroke flags (5 m out) are a handy ruler, 15 m is three flag-distances from the wall.

Breaststroke has no 15 m rule (one underwater pull-down per length), so this step matters most for freestyle, backstroke and butterfly.

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