Cross sea
（重定向自Cross swell）
![Cross swell at Île de Ré](/Images/godic/202501/07/Ile_de_ré3951.JPG")
In surface navigation, a cross sea is a sea state with two wave systems traveling at oblique angles. This may occur when water waves from one weather system continue despite a shift in wind. Waves generated by the new wind run at an angle to the old, creating a shifting, dangerous pattern. Until the older waves have dissipated, they create a sea hazard among the most perilous.