I did my best to stay away from wiki's and tutorial videos before playing this for the first time just under a week ago. I eventually capitulated around 10 hours in when I was really struggling to figure out how to get a Moonpool. Turns out, I needed to find an appropriate tech fragment and, after that, problem solved. Since then I've looked up about a half dozen things but tried to largely keep my experiences of the game to be drawn directly from the game. Here's my take:

The game is excellent, at least for the first few hours, at leaving you wondering what everything is and what it does while still allowing you freedom to poke and prod at your immediate environment without dying. Sure, the first dangerous critters are pretty obviously dangerous from afar and make a distinct roar before charging you, and aren't death-or-glory killbots so you can run away or scare them off. This makes for an environment you can experiment with, even in Survival mode where you need to manage food and water as well as health and oxygen.

The ocean looks and feels great. Motion washes in a way that feels pretty good, like you're in water (which, of course, you are). Basic resources aren't too hard to come by. Indeed, the biggest early restriction is oxygen, but you don't dive too deep for too long at the start and can always just come straight back to the surface.

There's a marker to show the direction to your escape pod on your HUD when you're roughly facing the right direction (and haven't gone a very long way from it). Makes it possible to get home even when you're still trying to figure out what to eat and what might kill you.

Radiation, from the crashed ship I believe, keeps you boxed in on one side and away from some really nasty predators that would literally eat you in one. You'll deal with that later. For the start, the radiation hurts and provides a soft "wall" to encourage you back to places more suitable for your (lack of) experience.

As you find more things, your fabricator -- the device on the escape pod you use to convert resources into useful equipment, cooked food, etc -- gives you more options. This is good in that you don't start swamped with options, a bunch of which aren't useful to you yet, but it's also unhelpful in a game otherwise lacking a tutorial (at this stage). Means that you might know something exists (for example, the Moonpool) but not see the option to build it anywhere. That's fine in that one of this game's strengths is exploration and discovery, but also confusing. Perhaps an option to show unavailable construction options might help? In any case, while the game is Early Access, the wiki and an occasional youtube video should get you through the rough spots where you're missing the prerequisite item that reveals the appropriate construction option.

I deliberately waited a long while to make sure that this game was both receiving regular updates and was in a stable, playable state. I'm pleased to report that the game seems very stable after 20+ hours of play. There's a few performance drops now and then, though rarely for more than a couple of seconds, even on a very high power computer (i7, 2x 970's, 16GB RAM, SSD), and I notice some report more regular performance issues but I've not really seen them. Optimisation is usually a late stage process in development so I'm not worried. Thus far, no crashes or serious glitches whatsoever for me.

The ocean is surprisingly large and your ability to explore is somewhat capped by what equipment you've built so far. I find you have to push to the edges of your exploration capability to find the new resources you need to make getting there easier in future. Often you're looking for a new tech fragment, or a resource that only appears in a particular area, or below a particular depth. But by shifting areas or depths you come across more dangerous environments, not least of which is that you need somewhere to retreat to in order to refill your oxygen (and empty your inventory of resources you've collected). By inference, I believe I've seen less than half of what there is to see, perhaps only a third, though admittedly I'm cautious so I tend to take fewer risks than I could. My deepest dive has been around 550 metres, with my deepest base at around 450 metres. I believe one can get a lot deeper than that...

So, to sum up, or tl;dr ...

An excellent underwater exploration game that manages to be somewhat gentle in the beginning, while offering more for more risk (or just more guts, I guess). Stable, looks good, still a few bugs here and there (easily reported from within the game), but very playable and worth your time to investigate. Developer is active and open. I eagerly look forward to future updates. Think I'll be back to playing next, actually... :)