Content-wise this patch includes two new maps, combat-affecting weather, and a boatload of ship changes. The sights and sounds of WoWS also received updates. Acoustic improvements include new music tracks (some with vocals), better aircraft engine sounds, the ability to control gunfire volume, and much more. The visuals were spruced up with new rendering shells, more impressive sinking ships, and full-screen fire effects. You can get a walkthrough of these changes in the video below, or read up on everything in the official patch notes.
Source: Patch notes, premium offer; thanks to ThatLanteshGuy for the tip!