Looks like a jurisdiction thing–a Canadian ship launched it though.

The submersible was reported missing after it was overdue by a couple of hours on Sunday evening, according to Chief Mi’sel Joe — head of the Mi’kmaq band which owns the ship from which the submersible is launched.

https://www.cbc.ca/news/canada/newfoundland-labrador/titanic-submarine-missing-search-1.6881095?cmp=rss