Dr. Seuss' characters aren't the only Christmas Whos on display this year, as the BBC has just announced the early UK release of Shadows of the Vashta Nerada, the fourth and final downloadable episode of the first season of Doctor Who: The Adventure Games.

Shadows of the Vashta Nerada picks up immediately after the cliffhanger ending of Episode 3, as the Doctor and Amy "materialise just south of London (and about a 1000 miles to the left) inside an aquatic sea-bed colony called Poseidon". With the episode taking place entirely underwater, the pair face their most terrifying foe yet, in the form of a 50-foot alien shark.

Originally slated for a Christmas day release, the new episode is available now for both PC and Mac free of charge from for UK residents. The rest of the world will need to keep waiting until its commercial release on Direct2Drive for a cost of $4.95. While no specific date has been confirmed, the delay isn't expected to be as long as it was for the first three episodes.

For more details about the series, or to download the game for those in the UK, head on over to the official website.