Gameplay in Endless Ocean: Luminous is based around exploring procedurally generated sections of the Veiled Sea, scanning the marine life, and salvaging any pieces of treasure you come across. Each map is divided into a number of grid squares. As you explore each zone in the grid, the topography is revealed – exploring 80% of an area unveils the rest of its map and unlocks that particular section’s Dive ID, allowing you to return to it later or share it with friends.

Maps contain a variety of aquatic structures, such as sunlit reefs, rocky plateaus, and murky caves. There’s a tonne of verticality to traverse, taking you from the tropical shallows way down to the pitch-black depths. You’ll also encounter different biomes with distinct inhabitants; freshwater or arctic waters play host to unique marine life, while ancient underwater ruins play host to forgotten creatures from the deep.

My first foray into the deepest parts of the Veiled Sea was absolutely terrifying. Your torch covers just a few metres in front of you, illuminating some of the ocean’s most alien creatures only when they’re right in your face. Thankfully, all of the creatures in Endless Ocean are completely docile — the “light” makes them calm, so you’re never in any danger. This doesn’t help to offset the completely rational thalassophobia you might experience mid-dive, but it does mean that the occasional shark-infested abandoned shipwreck becomes an enticing landmark rather than a site to avoid.

As you explore, your main activity is scanning marine life. It works pretty much exactly like Samus’ Scan Visor in the Metroid Prime series (aim and hold L to scan), but you’re able to scan multiple creatures at once before the camera zooms in and displays details of everything you’ve recorded. It’s… pretty clunky, to be honest. Every fish is shown in an enormous list that can only be scrolled through one at a time. Focusing on a fish displays options for tagging it, inviting it to swim with you, or receiving a detailed description of what makes it unique (read aloud by your trusty AI companion). Time is not paused while you’re scrolling this list, meaning you’ll sometimes see schools of unscanned fish flitter past while you’re mashing B to exit the scan interface.

Aside from the story missions, diving adventures occasionally present miscellaneous side quests that unlock panels on the Mystery Board or summon Unique Marine Life (UMLs), which are special “undiscovered” creatures with unnatural abilities, such as turning transparent. These quests are usually very simple, involving scanning specific creatures or bringing particular fish buddies to a spot on the map, but they serve to break up the rhythmic routine of swimming and scanning with a bit of direction. You’ll also find treasure and artifacts scattered across each map, which reward you with currency when salvaged.

As well as its story and single-player Solo Dives, Endless Ocean: Luminous also offers online multiplayer Shared Dives for up to thirty divers at once. There’s not a huge difference in gameplay between diving alone or with mates (you’re still swimming around scanning fish and collecting treasure) but there’s an efficiency to exploring together that gives the feeling that the game was balanced around this mode in particular.

Unlocking 80% of the map is much faster with a group, as is clocking up scan-rates and completing quests. You can see each other’s tagged creatures or treasure, and the unlockable emotes encourage non-verbal interaction. Not everything is shared, however, and it was a little upsetting when my online Shared Dive squad managed to summon a UML only for it to swim away after a single player had scanned it.