Is it still considered archaeology when you're looking for human artifacts underwater? It sure is! It's known as marine or maritime archaeology. Marine archaeology is its own area of study due to its unique nature.
A marine archaeology excavation brings with it issues and challenges unique to being at the bottom of the ocean. For one thing, people can only dive so deep. For some wrecks, notably that of the RMS Titanic, remote controlled robots were used instead of fragile humans. The seafloor is a very dangerous place, it is also quite cold down there.
A brave robot, exploring the wreck of the RMS Titanic.
Artifacts and ruins left underwater are quickly covered in marine life.
“Remote controlled robots were used instead of fragile humans”