Siren's Rest is the first DLC for the excellent Still Wakes the Deep, in which there was a lot of underwater swimming. This story, set 10 years after the disaster aboard the Beira Delta oil rig is virtually all underwater diving, but thankfully this time you have 'hard hat' diving gear with air supplied through an umbilical from the surface via a diving bell. Playing as a young woman named Mhairi, along with your dive partner Rob, your task is to find as many of the crews' remains as you can, pick up any possessions you find to return to relatives as mementos, and also maybe find out what caused the disaster...
The underwater effects and the feeling of diving is exceptionally well done, but as atmospheric as it is, we didn't see a single fish, crab or shellfish.
As with the main game, Siren's Rest has some staggeringly stupid achievements, the first one being "play the game through in the Scottish Gaelic language" (which the main game also had) and the other being disconnect your umbilical so you asphyxiate after using all the remaining air in your suit! Quite why one of the dev team thought these were a good idea, God only knows–I guess it takes all sorts...
The game sometimes also removes directional control for a few seconds after interacting with something, which is a bit weird. The only other thing I'd gripe about is the amount of clipping–often seen where your character's hands disappear into the scenery. This is also very obvious with your umbilical, which would have got snagged here, there and everywhere but miraculously stays with you virtually throughout the mission (maybe because it can clip through scenery when it feels like it?) There are a couple of occasions where you have to disconnect it to find a way to continue, but making sure your umbilical was safely routed by giving it a tug every now and then could have been a major gameplay element, and made the game even more claustrophobically realistic.
Siren's Rest will probably take you 2-4 hours to complete, the more you explore the longer it'll take (duh). You're unlikely to get lost (thanks to the helpful waypoint marker available with a tap of 'LB') despite the almost constant dark, dingy settings, which is a good thing.
Gripes aside, this is one of the best DLCs I've played in a while, and only gets marked down for the scenery clipping and the daft achievements/trophies.
Many thanks to Secret Mode, The Chinese Room and PressEngine