Instead of divers, remote-controlled submersible craft would have to be used, but even that poses problems.

BBC: Analysis: Salvaging the Prestige

TOKYO Japan patrol craft spotted unidentified submarines just outside the country's territorial waters, prompting Tokyo to warn of security action if submersible craft enter its waters developments that could further aggravate strained tension with Beijing amid a territorial dispute.

WSJ: Japan on Alert Over Submarines Near Its Territorial Waters

TOKYO Japan patrol craft spotted unidentified submarines just outside the country's territorial waters, prompting Tokyo to issue a warning that it may order security action if submersible craft enter its waters developments that could further aggravate strained ties with Beijing amid a territorial dispute.

WSJ: Japan on Alert Over Submarines Near Its Territorial Waters