This level set has been in the making for quite some time, and I'm glad it's finally here for us to enjoy! For a first time level, this is extremely well done. The level design is very nice, with some nicely detailed ares to match attractive coloured lighting. Although it didn't totally feel like you were underwater for most of it, Burial at Sea was very finely constructed, along with a quite non-linear layout at times (although it could get a little confusing).
Gameplay was very well done too, with some very hectic sections such as when you need to use four scientists (much like Half-Life) to open a door for you while fighting off great batches of nasty enemies. The only let down was ammunition on this particular level (I think it was the third) dropped well down and I completely ran out of shells and bullets. But with plenty of Grenades I was able to eventually get back on top with ammo so that there was easily enough for the VERY nasty end battle.
This set of levels were a great pleasure to play, and yet another great release which you'll want to keep!