When I first played Abzû almost a year ago, I was introduced to its concept and acclimated to moving underwater in the general ecosystem that developer Giant Squid had created. Our recent hands-on with the latest build of the game, however, is just as intriguing of an introduction to its aquatic world. The studio has subtly refined parts of the experience to make it more inviting while also deepening the mysteries at its heart.

The first thing that strikes me is how natural it feels to move through the water and among the sea life. I hadn't played the game since E3, but it's easy to simply pick up the controller and swim around. I can now send out a sonar chirp when near fish to attract them and charge up my ability to boost forward while swimming, the capacity for which increases as the game progresses. "We added those mechanics to make players more excited to explore, because that's really the goal," says creator Matt Nava.

The new boost alone isn't what makes me want to explore. The movements of the animals themselves silently beckon. Grabbing on to them and hitching a ride is a simple mechanic that brings a rush of empathy. Their presence is amplified by a little extra visual sheen since I last played the game. Even when tens of thousands of fish converge into a whirling bait ball being torn apart by darting predators, Abzû looks amazing. The bait ball – whereby schools of smaller prey fish instinctively swarm together in a swirling ball to visually confuse predators and provide safety in numbers – is a phenomenon that speaks to the splendor and vibrancy of the world. I can swim within the bait ball but it also moves according to its own rhythm. I'm curious if any gameplay is attached to the ball, but for the moment it's simply an example of the dynamism of the environment.

Abzû's challenge is to strike that balance between encouraging freeform exploration but also making sure players progress. I have no problem with that in the build; I'm happy to wander around the opening areas, taking it all in and moving on when I'm ready. Currently the game has a simple 3D map players can bring up at any time to see the general direction of objectives, but the team isn't sure what form it will take in the final build. However, during my time with the game I only consult it once or twice.

I find and dig up a few drones down on the sandy sea bed. They come online, scanning and recognizing something in my face, which activates their dormant programming. Following me around, they dig up some sand bars and drain resource pools with telescopic tentacles, further charging my boost reserves and leading me into new areas.

Each region feels different than the last, some with all new creatures, colors, music, and the heightened expectation of the journey still ahead. One underwater cavern opens up to reveal an impressive seascape teeming with life and masses of coral. Swimming around, I find an opening to a partially concealed area that Nava tells me will contain secrets when the game releases. For now I move on, joining a school of fish riding a current out to parts unknown.

Despite the vastness of the sea, Abzû is not an open-world game. Instead, it aims to encourage exploration and convey the enormity of the ocean but avoid players getting lost or the need to backtrack. "We want the player to explore a specific area and feel free to do that," Nava says. "Once they finish that area and go on to the next one, then they don't have to think about it anymore. They can keep going forward." The area I just left contained other currents to different locations, but in the end, the developer wants players to experience a linear story.

Even in these early sections of the game, my curiosity about larger events is piqued. I start off floating seemingly lifeless in calm waters, the sky a vista above. It's a different perspective to what I imagine will be a majority of my time spent underwater. Upon diving below it's not long before I encounter architectural remnants of some previous civilization. More than just sunken structures reclaimed by the water, these are arches and columns integrated directly into the coral and sea bed. I even come across carved busts of sharks. Were these meant to be worshiped? I can interact with them, but Nava doesn't reveal their function. In another area I use the drones to clear away sand from a wall of hieroglyphics. Unfortunately, I can't decipher the meaning of the scene.

Perhaps the most intriguing part of my experience with the game, however, is not my questions about who built the structures, but rather my interactions with the sea creatures. Later in the demo I come across a blue whale slowly making its way down into the depths, singing a lonely song. I'm immediately drawn to the impressive mammal, and as I grab onto it we plunge into the alien surroundings.

Later, I'm near the bottom of the ocean, which is an inhospitable environment and home to very specialized species evolved to survive the pressure, temperatures, and thermal vents. The entire level is cast in a murky reddish hue; the frolicking near the placid surface is now a distant world. Down here, Abzû's adventure is just beginning. "There's a lot of secrets we're hiding down there," Nava says. "A lot of things that are going to surprise in the second and third acts."