Tidal bore
（重定向自Eagre）
![Undular bore and whelps near the mouth of Araguari River in north-eastern Brazil. View is oblique toward mouth from airplane at approximately 100 ft (30 m) altitude.[3]](/uploads/202501/10/Undular_bore_Araguari_River-Brazil-USGS-bws000263417.jpg)
A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay against the direction of the river or bay's current.