Cohort progression — Pływamy i Ratujemy Ustronie Morskie
Median season-best times of each birth-year cohort, overlaid by age — shows how consecutive groups developed at the same stage of training.
Event: 50 freestyle100 freestyle50 butterfly50 backstroke200 freestyle50 breaststroke100 unknown100 backstroke50 unknown50 manikin carry25 freestyle100 butterfly25 unknown25 backstroke100 medley400 freestyle100 breaststroke200 medley100 manikin carry with fins50 manikin carry with fins