Organisers say that the bull 'became agitated after its horns were set on fire' and it dived into the sea. It tried to raise its head out of the water but was unable to do so and drowned very quickly.
Onlookers say it was clear the bull had no strength and was unable to swim.
They added that a boat used to guide the bulls back to shore after they enter the water was unable to save the beast. The crew of the boat grabbed the animal's horns and held its head above water but by that time it was beyond help.
Jávea councillor Pepa Chorro, who was responsible for setting the bulls horns on fire, said 'it seemed very nervous' but she put this down to it being the first time it had participated in the fiestas.
She added that after its horns were alight it took no more than five minutes for the animal to dive into the sea, but due to its very tired state it was unable to stay afloat and all efforts to revive it were in vain.
The incident occurred a little after midnight on Tuesday.
Organisers say the bous al mar fiestas now included the bous embolats (attaching fire to horns) tradition, something that is not normally part of the Jávea fiestas.