We know for sure that there are deposits of natural gas in the earth. In theory, natural erosion might eventually allow one to escape on its own. However, it's not at all clear why this would happen on the bottom of the ocean, an environment more favorable to deposition than erosion.
At any rate, if I understand the article, methane is laying around already exposed on the sea floor in semi-stable hydrate form, just waiting for some odd event to turn it into a huge gas bubble. If that's true, there's more untapped energy out there than we thought. The problem is that someone should have put the whole business on a more solid observational basis by this late date than seems to be the case.
The area shown in the map on an earlier post is conincident with significant North Sea oil, natural gas, and gas condensate production. It is no surprise that methane degassing occurs there.
In the Santa Barbara Channel, off of the coast of California, there is an area near "Coal Oil Point" with prolific natural gas (95%+ methane) seeps. Two 100 ft x 100 ft steel pyraminds were lowered on to the seafloor to capture gas eminating from one very active area. These two underwater tents capture enough natural gas to power the domestic natural gas needs for a city of 25,000 people each and every day. I have been on boats in the midst of these seepages. It is like floating in a oily Coca Cola. And I lived to tell about it!