submersible

noun
  1. 1

    A small nonmilitary, non-nuclear submarine for exploration.

  2. 2

    A retroactive term used for non-nuclear submarines; nuclear submarines are termed "true submarines".

  3. 3

    A term used primarily by some navies for nuclear submarines, termed "true submersibles", because they cannot retroactively declare that their non-nuclear submarines should be called by a different name.

  4. 4

    A very small "baby" submarine designed for specific localized missions, usually while tethered to a submarine or ship for life support and communications. Slang synonyms: midget-submarine, anchor.

adjective
  1. 1

    Able to be submerged.

Source: https://en.wiktionary.org/wiki/submersible