Sea of Thieves was announced during Microsoft's press conference at
E3 2015, with Duncan describing the game as the "most ambitious project" from Rare. Initially set to be released in 2017, the game was delayed to early 2018 to allow additional development time. Microsoft marketed the game extensively. Players who pre-ordered the game received the Black Dog Pack, which included exclusive cosmetic content and access to a closed
beta. Players could also purchase a separate
Sea of Thieves-themed Xbox
wireless controller, and anyone who purchased the
Xbox One X console from 18 to 24 March would receive a free digital copy of the game. Microsoft's Australian branch partnered with music band Captain Hellfire & The Wretched Brethren for a two-day event in which the pirate band sang different
sea shanties requested by players. The program was broadcast via
Facebook, Mixer, and Twitch from 24 to 25 March 2018. Microsoft also launched "The Quest", an
alternate reality game where players needed to solve different riddles. The winners would receive one of four golden bananas (each valued at £20,000) as rewards. Rare also hosted a competition which tasked fans to create
achievements for the game. Several
stress tests and betas were released ahead of the game's official launch on 17 March. At launch, many players reported that they could not log into the game. Duncan said that Rare underestimated the server capacity as the number of people logging in to play the game during the launch period was unexpectedly high. Various fixes have been released to improve the game's online infrastructure.
Sea of Thieves was released on Steam on June 3, 2020, and reached the "global top sellers" list in the same week. The game was released for the
PlayStation 5 on April 30, 2024, as part of Microsoft's strategy to bring some of its games to rival platforms. It went on to become the platform's most downloaded game in North America in May 2024. In addition to being a retail release,
Sea of Thieves is an
Xbox Play Anywhere title and the game was made available for
Xbox Game Pass subscribers at launch. However,
crossplay between PC and Xbox One players was made optional in February 2019 to ensure that all players feel that "they have a level playing field". On PC, the game was initially only available through Xbox Game Pass and
Microsoft Store before Microsoft announced a release for
Steam in April 2020. Players began to set rules, develop their own sets of challenges, and host their own events. To further encourage these players, Rare announced plans to incorporate
private servers into the game.
Downloadable content Rare envisioned
Sea of Thieves to be a "
game as a service" and expected it to continue receiving updates for ten years. After the team had fixed most of the technical issues, they began looking at players' feedback and identified that players were complaining that there were not enough activities for them to participate in. Chapman stated that the team's strategy was to give players what they want, ensure that they fit within the
Sea of Thieves universe, and "surprise" players. Rare has four teams of employees working in parallel to create the game's various expansions so that large content updates can be released frequently while ensuring that sufficient development time can be given to each team. The team hoped to release a large content update every six weeks to two months, and used "Bilge Rat Adventures", which are time-limited challenges, to fill the gap between each expansion. The ultimate goal was to make the game "as big and successful as it can be". The first major expansion,
The Hungering Deep, was developed within two months. The second expansion,
Cursed Sails, introduced skeleton ships controlled by
artificial intelligence (AI). Despite being adamant about not doing so prior to the game's launch, the team decided to implement the feature as it was one of the biggest fan requests. All the expansions are free of charge as they did not want to divide the player base. ''Smuggler's Fortune'', which was released in September 2019, added the Pirate Emporium, a new store that supports
microtransactions. A new type of currency named "Ancient Coins" can be purchased from both the Xbox store and in-game. Rare released monthly updates and introduced new Tall Tales, new modes, new quests, and new features until December 2020. In December 2020, Rare announced that they would move away from producing monthly updates for the game and instead, adopt the "battle pass" model popularised by games such as
Fortnite and
Fall Guys. Each season, which would last for about three months, would introduce new content or new ways of playing the game, with live events being hosted regularly. Rare also introduced the "Plunder Pass", an optional premium tier that grants players additional rewards which does have free options. The first season began in January 2021 and Season 2 began in April 2021. Rare also announced that they would stop updating the Arena mode as the vast majority of the players spent their time playing the cooperative adventure mode. Arena mode was shut down in March 2022 after an announcement earlier in the year. Rare described 2022 as the "biggest year yet" for
Sea of Thieves, and the studio planned to add more features, including Adventures, which are story-driven live events that last for around two weeks, and Mysteries, which would unfold over the course of several months. Each adventure was designed as a chapter in a long story, as the team hoped that these live events can "bring a sense of continual danger to the world". Mysteries were inspired by
alternate reality games, in which hints would be given to the player both in and out of the game.
Sea of Thieves saw frequent collaborations with other Microsoft franchises. The Bird and Bear Figurehead, based on Rare's own
Banjo-Kazooie series, was released in July 2018. Ships based on the
Halo series and the
Gears of War franchise were released in June and November 2019 respectively, as well as a ship set based on
Ori and the Will of the Wisps released in March 2020. Rare also expanded
Sea of Thieves to other media. It had partnered with
Mongoose Publishing to release a
tabletop game titled
Sea of Thieves Roleplaying Game in October 2019.
Titan Comics debuted a comic series written by
Jeremy Whitley in March 2018.
Titan Books also worked with Rare to publish an art book named
Tales from the Sea of Thieves. A free expansion titled ''A Pirate's Life'', which is based on
Disney's
Pirates of the Caribbean franchise, was released on June 22, 2021, and spans five Tall Tales. The expansion was in development for about two years. A second free expansion titled
The Legend of Monkey Island, based on
Lucasfilm Games'
Monkey Island series, was released on July 20, 2023, and spans three Tall Tales. ==Reception==