not that new really. there was something like this from Eastern Front Studio (Fathoms Deep?) which never was too much of a success, then there was something from Eric Louchard, then the whole Deep Wars game (now on kickstarter) which the miniatures are most likely sculpted for. In the meantime there was one manufacturer of really good lizard models and some underwater monsters. can't recall the name now but I liked them a lot.
Eastern Front Studios - true, though they didn't have any game behind the minis, IIRC.
Eric's stuff (Dragonblood Miniatures) had no game and were sold to Antimatter Games for this game.
Not sure about the Deep Water game you mentioned, never heard of it. they are still on the kickstarter? this Shadow Sea game was released earlier (already available), so it is actually something new.
oh... so Eric Louchard sold his range to Antimatter Games, which is a company run by ... Eric Louchard.
and that company releases Shadow Sea game first, and now they want to release Deep Wars which is set in the Shadow Sea universe...