All Blue

All Blue (オールブルー) is a mystical sea of legend, rumored to be the only place in the world where the North, South, East, and West seas meet. In this legendary ocean it is said that there are fish coming from each of the seas; and to have such a resource at one's disposal is the ultimate dream of every chef. Sanji strives to find this ocean of dreams. It is said that the All Blue is found in the Grand Line. Zeff saved Sanji when he realized that they had the same dream of going to All Blue. In the 4Kids anime it's called the Great Blue. Although All Blue have yet to appear in the series, it was first mentioned in Chapter 56 and Episode 26, where Sanji and some chefs discussed if All Blue even exists.

In a Water 7 filler episode, Sanji finds another hint of the All Blue's existence: salt from the All Blue is brought from the Aqua Laguna and is shown to be such a good seasoning that even a small amount in food is enough to outclass even his own cooking. He later gathers all the All Blue salt and begins using it in all of his cooking. However, this cannot be considered canon.

Upon reaching Mermaid Cove in Fishman Island, Sanji exclaims to the crew that he has found All Blue there. However Usopp asks him whether it is certain, thus it has not been confirmed whether Sanji had really found All Blue (and this most likely just an exaggeration, due to him being excited to see mermaids). However Fishman Island, being on the exact opposite side of the planet in relation to Reverse Mountain, means it's possible for the four seas converge to that place.