Note: This story was only released separately in the US. In the UK and Australia it was released as part of the Beneath the Surface box set instead. Mat Irvine's first name is mis-spelt as "Matt" twice on the back cover blurb.
Earth, 2084. Two global superpowers hover on the brink of war. When the TARDIS is forced to make an unplanned visit to Sea Base Four, the Doctor, Tegan and Turlough find themselves accused of being enemy agents. Quickly embroiled in a deadly game of paranoid intrigue, it becomes clear that others on the base have sabotage and murder in mind. However, there is a greater threat to humankind: the Silurians and Sea Devils, prehistoric reptiles seeking to reclaim the Earth. Can the Doctor prevent them from implementing their "final solution" and triggering a war that could wipe out the entire human race?
DVD EXTRAS INCLUDE:
- Commentary by actors Peter Davison (the Doctor) and Janet Fielding (Tegan), script editor Eric Saward and visual effects designer Matt Irvine
- The Depths Making Of with cast and crew interviews (31 mins)
- They Came from Beneath the Sea Featurette on the realization of the Silurians, Sea Devils and the Myrka (13 mins)
- Science in Action Matt Irvine discusses his effects work (6 mins)
- Trails and Continuities (4 mins)
- Isolated Music
- Radio Times Listings (DVD-ROM PC/Mac)
- Photo Gallery (7 mins)
- Production Note Subtitles
- Digitally remastered picture and sound quality
Originally transmitted January 5 - 13, 1984