From The Stargate Omnipedia
A Russian Foxtrot-class attack submarine. One such submarine intercepted the downed Asgard
had disabled its deceleration drive
, forcing it to plummet into the atmosphere and the Pacific Ocean.
This particular Blackbird submarine was overrun by a single Replicator, constructed of Asgard alloys. It entered the vessel through a torpedo tube and killed the entire crew.
Within hours the single machine had created unmanageable numbers of Replicator blocks. The Blackbird was subsequently destroyed, preventing the Replicators from escaping to infest Earth.
Small Victories - A Replicator infiltrates a Russian Blackbird submarine, killing her crew and making additional Replicators with the tehnology.