Barclay makes a terrifying descent into the world of Homo Aqua. Back on the land, Kate stands alone as Downing Street conspires with the army to change the course of the war.
| Name | Type | Role | |
|---|---|---|---|
| Pete McTighe | Writer | ||
| Manpreet Bachu | Guest Star | Ravi Singh | |
| Gethin Alderman | Guest Star | Homo Aqua | |
| John Addison | Guest Star | Captain Daniel Gaitz | |
| Charles Sandford | Guest Star | Homo Aqua | |
| Teri Ann Bobb-Baxter | Guest Star | Commander Olivia Harper | |
| Patrick Baladi | Guest Star | Sir Keith Spears | |
| William Gaminara | Guest Star | Ted Campbell | |
| Seeta Indrani | Guest Star | Priya Lakhani | |
| Dylan Holmes Williams | Director |