AbstractMeasurements of vertical erosion of till in water depths ranging from 1.1 m to 5 m have been obtained using a modified micro‐erosion meter. Measurements in this environment are hindered by poor underwater visibility and losses due to high erosion rates and ice action. There is considerable spatial and temporal variability in the erosion rates measured but average values show a general increase from 11 mm y−1 in 6 m of water to about 35 mm y−1 in 2.3 m of water and even higher rates closer to shore. The measured values in shallow water are in good agreement with long‐term rates extrapolated from shoreline recession. It is suggested that erosion occurs through abrasion and fluid stressing, and that these mechanisms are aided by softening of the upper surface of the till, possibly through cyclic ‘fatigue failure’.