Game is called Fishing Planet and is available right now on Steam, still in development but has hours of content and is ridiculously fun... if you like fishing.
To save you time reading... the game is a good fishing simulator, so it ain't too arcade like...so no rock music blaring with a voice over shouting 'FISH ON!!' while you crank in the fish... its real quiet (too quiet actually), its more like real fishing in that its relaxing and chilled with some excitement when you realise the fish you hooked may be a decent size.
If you plan to be all MLGPRO 360 no scope headshot casting fish in e-Tourneys... wrong game for you mate

To those still reading...
Game is well presented with a reasonably simple UI, not overly complex yet still manages to provide a large array of proper fishing options in the form of equipment and tackle.
There is a progression system where you 'level up' and gain experience and credits for fish caught, achievements and simply logging on... oh yeah its online only, each player connects to central servers and all player data and fish data is stored on the server, no local data hacks but luckily each player gets a instance of the fishing spots to themselves, and only see other players in the chat box... no troll jumping in your face or casting over you, just you and the water.
It isnt very hard to start in, and is easy to get going initially but does get a little slower later but if you relax and enjoy the fishing rather than trying to grind levels you shouldn't have any issues with progression.
The business model is currently VERY generous, hell too generous as even the premium currency cannot be bought by real cash, you can only buy equipment packs in the form of DLC, credit packs to give you credits (which is the none premium currency) and premium membership which only boosts your exp and cash game... basically boosters.
The premium currency is coins (or gold) which is earned by catching unique classes of the various fish, leveling up, logging on 5 days in a row... may be other ways, I didnt notice I just fished and saw I had x amount of 'em, but you cant throw money at the screen and get 'em (yet, maybe the devs will add this, not mentioned though).
The coins buy special equipment and bait / tackle that is better than none premium stuff but isn't mandatory to have, just makes it easier and as mentioned you need to earn the coins and cant simply slap the game with your wallet.
Game itself is on the Unity engine but looks fantastic, I couldn't believe it was on Unity, the spots are so atmospheric, the water looks great, the line mechanics are awesome (you can see your line float on drifts, hang over some obstacles, react to bites, coil up if you dont keep up with the slack ), the ambiance is great too (if somewhat annoying in some spots with repetitive bird calls and fly buzzing).
The gameplay mechanics are solid with a few minor gripes that the devs have said they are looking into, and with the minimal UI elements (which can be hidden totally), you have all the information you need to fish (even without the UI the line and rod reactions can let you know if something is biting or not).
The minor issues are mostly about how fish school in certain spots leaving vast amounts of the water bare, and many players search out youtube vids to find the spots and 'grind' fish there rather than actually...fishing.
Sounds are sparse, some are annoying (bird calls and buzzing flies) while most do the job ok, I do wish more was added but do appreciate the lack of arcade style sound effects and music... the sounds do make it nice and peaceful, and you can always run some tunes on your MP3 player

My experience with the game has been for the most part bug free and lag free, I haven't had issues as a result of it being online with the occasional idiots on the chat (which can be hidden, or the individuals ignored / reported).
I have waited for a while to make this topic as I didn't want to rush in, and gush over the game with early game enthusiasm but at 90 hours in I can still easily recommend the game as long as you understand, its Fishing... if real life fishing doesn't appeal one bit...this game wont change that at all.
It is probably one of the best fishing simulators currently out there, and its early in its development and much more content is planned... by all signs, it looks like it can only get better.
Fishing Planet , on Steam , 64 bit client with an experimental 32 bit client, registration is quick and easy and not intrusive at all but currently 1 account for each Steam account (plans to fix this is in the works, according to the devs).