A colloidal suspension of methane in water. This is sort of like chemically-formed shortening.

Imagine that. Undersea Crisco.

Methane hydrates form when methane gas, percolating through the sediments under the sea floor, react with the water under extreme pressure.

Large deposits of methane hydrates can be found at the bottom of the Gulf of Mexico. There has been talk about mining these things to extract the methane.

Occasionally, chunks of methane hydrate break loose from the sea floor and float to the surface. As the methane can only remain in suspension at the extreme pressure at the sea bottom, the methane comes out of suspension as it rises. When it gets to the surface, it is as a gas; bubbles make the water's surface churn violently. It also appears that large amounts of methane dissolved in water reduce the bouyancy of anything floating in it.

This effect has been suggested as a cause for some of the ship sinkings blamed on the Bermuda Triangle.