The multiplayer game sees players explore an open world via a pirate ship from a first-person perspective.

The game features a progression system that only unlocks cosmetic items as the development team wanted to encourage both casual and experienced players to play together.

Rare departed from its reputation for secrecy during Sea of Thieves's development, inviting fans to test early builds.

[2] Solo and duo players sail around in a nimble sloop while players playing in a group control a larger three-person brigantine or a four-person galleon cooperatively by assuming different roles, such as steering the ship, manning the cannons, navigating, boarding enemy ships, and scouting from the crow's nest.

[8] A competitive multiplayer mode named "Arena" was introduced in the Anniversary update, allowing up to six teams of players to compete against each other by gathering silver in smaller maps.

[10] Players can complete voyages offered by the game's three main trading companies: Gold Hoarders, Order of Souls, and the Merchant Alliance.

The voyages offered by the Order of Souls are combat challenges, in which players travel to islands specified by the quest to defeat waves of skeletons.

[17] Selling treasures to any of the three main trading companies, as well as Reaper's Bones or Athena's Fortune, earns the player reputation points, which unlock more complicated quests from each faction and additional purchasable cosmetics.

[19][20] When exploring islands players can find various resources: food like bananas, coconuts, and mangos, which restore their health, as well as wood planks, firebombs, blunderbombs, and cannonballs.

[8][6] When players are sailing on the ocean, they may sometimes face adverse weather conditions such as thunderstorms,[3] or encounter shipwrecks, messages in bottles, barrels, skeleton ships, ghost fleets, or two monsters: the megalodon and the kraken.

[29] After playing the prototype, Microsoft executives including Phil Spencer and Kudo Tsunoda agreed to green-light the game's development.

[38] "I love the idea of things happening in the world that literally can shape the ongoing fabric and lore of Sea of Thieves.

The team believed that if a narrative campaign was included, incorporating players' actions into the game's lore would become difficult.

Designer Mike Chapman believed a lot of parallels can be drawn between Sea of Thieves and The Goonies, in which a group of friends bond together while they search for treasure, creating a journey that all of them would fondly remember.

[44] Duncan added that the team chose this painted art style because they wanted it to be "timeless" and reflect the "joyful" and "delightful" game world.

[48] The maximum crew size is four as Rare felt that if the group was too large, it would not reflect a sense of "intimate friendship" and players might splinter off and hinder inter-player communication.

[29] In one of the game's early prototypes, players in the same crew can betray each other, though the feature was scrapped because the team felt that the experience was "horrible".

[52] 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.

Players who pre-ordered the game received the Black Dog Pack, which included exclusive cosmetic content and access to a closed beta.

[63] 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.

[79][80] The team hoped to release a large content update every 6 weeks to 2 months, and used "Bilge Rat Adventures", which are time-limited challenges, to fill the gap between each expansion.

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.

[88] 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".

Jordan Devore from Destructoid noted that with a full crew, the game could get chaotic and situations could turn volatile very quickly.

[112] Kyle Hilliard from Game Informer stated that each session "results in a story" due to the emergent gameplay, and praised Rare for successfully creating an excellent "pirate simulator" and "manufacturing a digital playground that is fun to explore".

[108] Brandin Tyrrel from IGN stated that "Sea of Thieves works well when treated like a chat room or a party game, where it serves as catalyst for having a good time with the people you're with".

[118] One of its writers, David Jagneaux, praised the Tall Tales and its riddles in his second review, which he described as "brain teasers that really challenge [player's] detective skills".

[109] In his summary, he wrote that the game is a "pirate fantasy sandbox with an enormous amount of things to do, made unpredictable and exciting by the addition of other players".

[130] In January 2020, Rare declared the game was "the most successful IP [Microsoft has] released in the generation", with it amassing more than 10 million players.