The race which first appeared in Doctor Who in 1972, the Sea Devils, whose history along with their reptilian land cousins the Silurians stretches back millions of years, are now known familiarly as Homo Aqua – but it’s not as simple as that.
There are several species of sentient aquatic beings collectively known as Aquakind.
Homo Aqua, the soldier-like beings formerly known as Sea Devils, have the scientific classification Homospondyl Erectus.
Closer to to humans in appearance, two characters called Salt (Gugu Mbatha-Raw) and Tide (Samuel Oatley) are classified as Homo Amphibia, the negotiators and the strategists of Aquakind.
There is another being with a tail seen as part of the Aquakind delegation to the worldwide summit in Empress Hall in London.
Showrunner Russell T Davies mentioned another being called Piscimorpha Grandis in Doctor Who Magazine.
As for the Myrka, a large aquatic reptile webbed feet and a tail used for battle by the Silurians in the 1984 Doctor Who episode Warriors of the Deep, they were almost seen in the series. Co-writer Pete Mctighe said in SFX magazine, that there was one written into the script of the third episode, The Deep — but the special effects budget was used elsewhere.
There’s no mention of the Hua-Shen, the sea dragon seen in the 2022 Doctor Who episode Legend of the Sea Devils.
The initial sighting of Aquakind happens in the first episode of the Doctor Who spin-off The War Between the Land and the Sea when a Homo Aqua is caught in a Spanish fishing boat’s net. In a frenzied panic, one of the crew member shoots their captive dead.
The most significant scene featuring Aquakind takes place at Empress Hall, a UNIT installation on the Thames in London. A waterway to a 94,000-litre water tank is hastily designed by UNIT scientist Shirley Bingham (Ruth Madeley) and jammed into the building after roughly knocking down the riverside wall. Aquakind swims up the waterway into the tank, then Salt exits an airlock to address humanity.
A delegation of humans must journey into the high-pressure depths of the ocean to the Aquakind habitat for further negotiations.
Some of Aquakind have pearls in their necks. According to one of the Homo Aqua actors Gethin Alderman in SFX magazine, “We see at points in the show how these have kind of a communal recorded memory within them. So we show stuff to the humans from here, but it enables us to see things that other members of the colony have experienced as well.”
Written by Russell T Davies and Pete McTighe and directed by Dylan Holmes Williams, The War Between the Land and the Sea will begin transmission on BBC iPlayer and BBC One in the UK on 7 December 2025. The spin-off series will transmit exclusively on Disney+ outside of the UK (where available) some time in 2026.