Trent Aegir
At certain times of the year, the lower tidal reaches of the Trent experience a moderately large tidal bore (up to five feet (1.5m) high), commonly known as the Trent Aegir (named for the Norse sea god). The Aegir occurs when a high spring tide meets the downstream flow of the river. The funnel shape of the river mouth exaggerates this effect, causing a large wave to travel upstream as far as Gainsborough, Lincolnshire, and sometimes beyond. The Aegir cannot travel much beyond Gainsborough as the shape of the river reduces the Aegir to little more than a ripple, and weirs north of Newark-on-Trent, Nottinghamshire stop its path completely.
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