Alderney Race

When the wind and the race current flow in opposite directions, the sea becomes particularly chaotic: wave heights can reach 4 metres (13 ft) and have wavelengths smaller than 50 metres (164 ft).

[2] On the contrary, when the wind and the stream flow in the same direction, the sea becomes calm, provided that the tidal coefficient is not too great.

The uneven seabed – both Alderney and La Hague lie in the Armorican Massif – makes the situation more complicated.

Bad weather can produce abundant wind-blown foam, making visibility poor.

During good weather, opposing wind and currents can cause breaking waves, especially at Banc de la Schôle and at Longis Bay in Alderney.