Recently, a dive performed as part of the NOAA’s Okeanos Explorer mission confirmed that underwater volcanic activity occurred in the Daikoku Seamount.

Experts have suspected that underwater volcanic activity occurred not long ago near the Mariana Islands. 
Recently, a dive performed as part of the NOAA’s Okeanos Explorer mission confirmed that there had, indeed, been such an event. 
Footage captured of the area, specifically the crater of Daikoku Seamount, shows volcanic smoke is still present, and venting is ongoing. 
Plumes of likely sulfur and carbon dioxide flow from the openings in crater’s lower wall and rim. 
The sulfur-heavy ground has drawn a diverse group of aquatic life.
Video shows the crater is occupied by flat fish, tubeworms, and crabs.