Bous a la mar is part of the Festa Major (Fiestas Mayores in Spanish) celebrated in Dénia on the second Wednesday following San Pedro. The celebration lasts the whole week with various events.
The week starts off with the cows running around town all the way to the port, which also happens on Friday. The most important day of the celebration is Wednesday. On that day, there is a religious procession honoring the Santísima Sangre.
Every day, people can participate or attend Bous a la mar (Valenciano; Toros al mar in Spanish, Bulls to the sea in English), where mostly young guys taunt cows/bulls and try to make them fall into the sea. It seems like the cows/bulls are better at it than the guys. However, all but one cow fell into the sea. I saw about seven total. The event takes place in an arena in the port of Dénia and takes place at 1 p.m. and at 7 p.m.
The festivities end on the weekend with a parade on Saturday and fireworks on Sunday night by the castle.
Here are some photos I took at Bous a la mar: