Aqua is a declarative CLI version manager. You list the tools you need — terraform, kubectl, helm, gh, hundreds more — with exact versions in an aqua.yaml file, and aqua install downloads them into a per-user cache and creates shim binaries on your $PATH. Run any tool and aqua transparently resolves it to the correct pinned version for the current directory.
Under the hood, aqua is a single Go binary that pulls from a community-maintained registry of package definitions (over 1,500 tools). Each registry entry describes where to download the binary for each OS/arch and, crucially, an SHA-256 checksum or Cosign signature. That makes aqua a practical supply-chain tool as well: every install can be checksum-verified, and you can enforce policies that refuse to install unsigned or unknown packages. It also generates lockfiles so CI and developer machines stay in sync.
In the broader ecosystem, aqua overlaps with asdf, mise, and Nix. Compared to asdf/mise it is narrower (binaries only, no language toolchains) but significantly faster and has better checksum handling out of the box. Compared to Nix it is drastically simpler at the cost of flexibility. It is a good fit for platform teams who want every engineer to run the same kubectl and terraform without writing bootstrap scripts.