section 3, page 18:
3.10. ABILITY OF THE DISSUB TO SIGNAL HER POSITION
a. The crew of a DISSUB may be able to indicate her position by one or more of the following methods:
1. Releasing one or two indicator buoys.
2. Firing Submarine Launched One Way Transmission (SLOT) buoys which transmit on VHF JEZEBEL Channels 25, 27, 29 or 31.
3. Firing an expendable communications buoy (ECB) or SEPIRB, which will transmit a SARBE DF beacon.
4. Firing yellow or white smoke candles or red or green grenades. The smoke candles may have fluorescent dye containers attached, which produce patches of green dye in the water, and may also carry a message
5. Transmitting her name in voice plain language and/or in SST mode on the UWT.
6. Transmitting on sonar, echo sounder, or by using emergency location beacons.
7. Hull tapping.
8. Releasing fuel or lubricating oil.
9. Switching on navigation or other underwater lights
They shouldn't have mentioned about the oil spill there are at least 10 other reasons i can list right now for the cause of oil spill.
Since they haven't reported and acoustical anomaly, indicating an explosion or implosion -bubble rise, it means the chances are still high for them to be safe.