Cook

Cooks (コック) are people who cook for passengers or crewmates on ships, or cook for customers in restaurants. All pirates can be hungry, so many of them need a cook to cook food to fill their stomachs.

Marine bases and Marine ships need them to feed the soldiers to keep them healthy. Commercial ships or cruise ships require them to feed the passengers.

List of Chef Jobs
For any character, particularly those traveling out to sea such as a pirate or a marine, the ability to feed themselves is a necessary aspect for survival. While it can be easy to get food, there are many problems presented: how to eat it, the edibility of certain artifacts (including the meat and plants on the mainland and the sea food in the ocean), means of preparation and, for the longer voyages, means of storage and rationing to allow the entire crew to survive between destinations. The purpose of a cook in the crew is to maintain edibles and crew survival between points. A good cook knows about the basics of all food taken on board the ship and the means to prepare it into something that can allow the crew to have something to eat. This cook also has a knowledge of the edibles and what to and not to eat on a voyage.

Cooks also have a key knowledge of the nutritional value of what to eat, allowing for the maintenance of good health of the crew and preventing common sea problems such as scurvy, making them responsible for maintaining the health of the crew, seconding only to the doctor. In fact, to a skilled cook, even the most rudimentary of ingredients can become the most wondrous and nutritious of meals. Finally, a cook is also the key behind the maintenance and stockpiling of food from the voyage and maintaining rations. While they are able to get their supplies from multiple sources, they are in charge of keeping watch on how much of what they have and making sure the crew gets enough both to allow for health and to make sure enough food is held through the journey.

Story
After the Syrup Village Arc, the Straw Hat Pirates met Johnny and Yosaku. Yosaku was sick from scurvy, so Nami instructed Usopp and Luffy to make soup to cure Yosaku. Yet the crew had no cooking experience, so Luffy decided to find a chef for his crew, although initially wanting a musician.

Baratie
Upon arriving at the Baratie, the ocean-going restaurant, Luffy met a man named Sanji, who was the assistant head-chef of the restaurant. There he also met the restaurant's owner, Zeff, along with two partners named Carne and Patty. Luffy was impressed with Sanji's compassion towards Gin and tries to get him to be his crew's chef, but Sanji refuses many times. After the battle with Don Krieg resolves, the cooks at the Baratie all claim Sanji's cooking is bad so he will leave and go with Luffy. Sanji eventually does, citing his dream of finding All Blue.

Trivia

 * On board real life ships, pirate, military or commerical, falling out with the ship's chef meant the meals could be affected.
 * Stealing food from the chef was sometimes considered amongst one of the biggest crimes at sea as it was the chef's duty to ensure the food on board lasted the entire journey.