Immediately off shore from New Orleans,LA there is a site of Gas Hydrate. Right in the same vicinity of the BP Macondo well oil spill. Could this be what has been breached and is now the cause of the bubbles and sink hole?

[link to pubs.usgs.gov]

You can see the red dot in the map. Dead smack in the middle of the area in question.

Excerpt;

Gas hydrates occur at many sites
along continental margins and in the Arctic
(fig. 1). Yet we know very little about
their composition, their volume, or the
best ways to exploit their resource potential.
The U.S. Geological Survey (USGS)
is investigating many aspects of gas
hydrates to understand their origin, their
occurrence, the factors that affect their stability,
and the possibility of using this vast
resource in the world energy mix.