Sea control is no longer sufficient, because the presence of submarine cables requires seabed control, which is much harder.
The NSR (Northern Sea Route) should not and need not be a Russian sea lane, and won't be if it has North Pacific and Nordic infrastructure.
China released DeepSeek, but is spending much greater effort in building the kind of navy and merchant marine needed to dominate at sea.
The U.S. Coast Guard confirmed a tragedy at sea - a very poorly designed submersible dived to a crush depth, and was crushed.