AQUAMAN. James Wan, director, co-story. David Leslie Johnson-McGoldrick, Will Beall, script, co-story. Geoff Johns, James Wan, and Will Beall, story — from the DC character(s) created by Mort Weisinger and Paul Norris. Bill Brzeski, production design. Australia/USA: DC Comics/DC Entertainment, Warner Bros. et al. (production) / Warner Bros. (distribution in USA and most of Earth), 2018; see IMDb for production and distribution details.
Relevant here for visuals in related sets.
To operate in air, Atlantans below the rank of vizier (apparently) wear armor with helmets supplying oxygenated (we assume) water. These should be compared and contrasted with the powered armor of Starship Troopers, The Forever War, and their successors.
To fight against the super-powers of Aquaman, the human antagonist constructs — if not from scratch — a fighting suit with some flight capacity, which in other fictive universes could be the precursors of the powered armor of Heinlein's Troopers. When sealed up, the suit's appearance is like that of a humanoid robot (see Leonard Heldreth's essay "In Search of the Ultimate Weapon: The Fighting Machine in Science Fiction Novels and Films"). The head of the suit resembles a preying mantis, for which see Thomas P. Dunn and Richard D. Erlich's discussion of insects and mechanisms in "The Ovion/Cylon Alliance."
The pre-Credits sequence shows a minisub — if a large one — attaching itself to a full-size Russian submarine. The sub is human-made and operated (produced by the US military, manned by human pirates), with a stealth-craft shape suggesting a ray or skate. The vessels (and other devices) of the Atlantans far more strongly take their shapes from undersea creatures, including one small craft that looks like a combination of pufferfish and stickle-back fish. The point is not developed in the film, but the set of images blending the mechanical with fish and other aquatic animals is possibly the one serious SF point of a film with interests other than science fiction.