We’re often told by veteran designers that the best game stories are the ones told, and experienced, by the players themselves. The little moments of personal drama, victory or tragedy that happen to you and only you while exploring a world, can be more memorable than any big cinematic crescendo.

Sea of Thieves, the online co-operative pirate adventure from Rare, is a game based around those moments. It isn’t just about sharing tasks, it’s about co-authoring stories. At the beginning of the game you’re thrust into a galleon with a small group of other players, and from here you must explore the ocean, using treasure maps to locate islands loaded with loot, before digging up the goods and clearing the heck out. At any moment, however, the game’s seamless multiplayer system may throw another ship full of players into the same waters – they may fight you for your gold, trade with you or suggest an alliance, but it’s all planned and decided by the players themselves.

A half-hour hands-on demo at Microsoft’s pre-E3 showcase provided a very short glimpse of co-operative pirating, but it was a hugely entertainment ride. While aboard the ship, players can freely wander the deck and below deck areas, but if you want to get anywhere, someone has to raise the sails, someone else must navigate and another player must steer. Using headphones to chat, you work out everything together, and need to collaborate closely to get moving. The key thing is deciding where to go. A menu brought up on the right bumper button shows your current treasure maps, as well as riddles – fiendish puzzle adventures which require you to decode a short verse in order to locate a hidden stash of goodies. According to the game’s producer Joe Neate, this element was designed with Twitch/Mixer streams in mind, allowing viewers to get involved in the riddle-solving fun via the live chat window. It’s a clever feature, revealing how closely the game has been designed with streaming in mind (throughout the development process, Rare invited dozens of YouTubers and streamers to their offices to test the game and suggest alterations).

Facebook Twitter Pinterest Here be skeletons. Photograph: Rare

This is a game about talking and sharing tasks. To navigate to an island players must use the large world map in the upper deck, and shout out directions, but there is no live marker on the map displaying your boat’s position – instead, you need to use landmarks and a compass to navigate, accentuating the need for close co-operation and also making the art of finding your way around feel more authentic. Your boat also has two rows of cannons for ship-to-ship combat, and you’ll find barrels of bananas (for health) and grog (for the opposite of health). When you’re not helping to steer or navigate, you can just wander about, perhaps using the items menu on the left bumper to select your accordion for a quick sea shanty, pressing the right trigger to belt out a song. It’s daft and pointless, but once you’ve watched a pirate being chased around his own ship by a marauding group of squeeze box enthusiasts, you’ll wonder how games have survived for so long without this feature.

When you reach an island, you need to drop the anchor then swim ashore, being careful to ensure that the ship is a safe distance from land – and the sharp rocks that surround it. We anchored way too close to the island we visited, and then swam to the beach just in time to see our boat sink into the brine. If that happens, a mermaid appears in the water nearby, offering to take you to a new boat, so you’re not stranded forever.

Once again, navigation is via a map that only gives you basic information about the area, complete with red X marks to show the whereabouts of treasure. You can wander about, sloping along the beaches or venturing inland to caves, jungles and steep cliffs. The mannered visual style makes for a simple yet colourful environment – it’s not the most picturesque game, but again, the fun and immersion is made by just being with people and exploring together – if it’s dark you’ll need one person to carry a lantern, but then if skeletons rise from the sand and attack, you’ll need someone with a cutlass or flintlock pistol (all accessible from the item menu). In some ways, the running and fighting moments feel a little like Left 4 Dead, with a densely clustered groups of players working together to spot loot and see off enemies. Except here one of you can just whip out an accordion and play tunelessly along to cut the tension.

Facebook Twitter Pinterest If an enemy attacks, you’ll need your trusty flintlock pistol. Photograph: Rare

We managed to make it to an X, using spades to dig up a chest, which someone then had to carry to the boat protected by the others. This treasure is never really safe – another team could be transported into your world, just in time to steal the box away, either while you’re on the island or back on your own boat. “The chest is a real object in the game world and can easily change hands,” says lead designer Mike Chapman. “You get all these memorable adventures where you come across another ship, sneak onboard, while trying to be as quiet as possible (the game has a proximity chat system, so the rival crew will hear you if you shout), get down to their lower deck and find tons of chests because they’ve been out on their own adventures. You get to steal that and have your pirate moment.”

We didn’t meet anyone else and according to Chapman you’ll be given several minutes to acclimatise to the game before there’s a chance of an interaction. “You might go half an hour without seeing another crew – that’s something we’ve been actively testing. For example, we pushed the draw distance right out so you get to see another ship from further away. It’s not about forcing contact – you don’t have to fight, or talk or trade; it’s about just feeling the presence of other players in the world.” In some ways, the system sounds a little like Journey, Thatgamecompany’s mystical adventure where online players would be paired together in a world, and could either attempt to interact or just work alone watching the other participant doing their own thing. Sea battles will certainly be a key element though, which is why the cannons are there – it looks like you can even load yourself into one and blast yourself on to the enemy craft. Your treasure is only banked when you get to an outpost, where the money is shared between your crew and can be used to customise your weapons and items.

When you die in the game your character is temporarily transported to a ghost ship, a sort of in-game lobby where dead players from other crews will all congregate and maybe even discuss their quests – and deaths. “You could form a bond, make a new friend and decide to form a crew together,” says Chapman. “We’re making all these design choices where you really do want to meet people and work together, it doesn’t have to devolve into combat. We want to make the most fun, welcoming multiplayer experience.”

Facebook Twitter Pinterest Boats come with two rows of cannons for ship-to-ship combat. Photograph: Rare

Along the way, there’s a lot of laughter and joking. The characters all look like stereotypical storybook buccaneers, blundering about the boat or through dark caverns getting into each other’s way, getting lost. Sometimes people get separated on an island, sometimes they accidentally fall off the ship while it’s sailing along so everyone else has to drop the anchor and help you aboard. In the trailer shown at the Microsoft press event on Sunday, it was clear that there are also sunken ships to plunder for treasure (avoiding the sharks), and hopefully Rare will add new islands and quests as you go along.

Of course, the success of the game will depend on how easy it is to find an entertaining and friendly crew – not everyone will have the luxury of playing with friends. There also needs to be a rich variety of quests and enemies to keep things afloat beyond the hilarious opening hours. We only saw skeletons on our island romp – there must be others; players will need to feel like there is much to discover out there on the ocean. Interesting competition is coming in, too, from games like Worlds Adrift and Ubisoft’s newly announced Skull and Bones, which uses the Assasin’s Creed 4 engine to bring much more visually rich and detailed sea battles to life. They may well prove more compelling and deep. We’ll see.

But it feels like there is something uniquely entertaining about this co-op game, drawing on all of Rare’s expertise at creating warm, welcoming worlds. It is a game very much for the YouTube/Twitch generation, a game to be watched as well as played, a sweet, good-natured game to share and laugh with. Among the bullets and bodies of the E3 press conference season, this is something to be treasured more than any buried loot.

Sea of Thieves is released on PC and Xbox One in 2018. Keith Stuart travelled to E3 with Microsoft, who covered his transport and accommodation costs.