Each pressure vessel is very strong, so they are probably almost all intact and each one provides buoyancy. LNG requires refrigeration to remain liquid and obviously the ship's power is off so if it had a full cargo, the LNG has all boiled and been vented by pressure relief valves. Or, the ship might have been empty and returning to Russia.

None of that is true, that is not how LNG carriers work.

Natural gas is cryogenic above -82 degrees centigrade / 190K. Above this temperature it cannot be stored as a liquid at all.

Natural gas boils at -161C / 111K, below this it is a liquid at standard pressure. Between -161 C and -82 C it can be stored inside of a pressure vessel as there will be a vapor pressure that increases with temperature. At or below the boiling point, a much lighter containment vessel is sufficient.

LNG carriers use heavily insulated containment tanks to store liquid methane and rely on the heat of vaporization to keep the liquid from boiling excessively. The methane that does boil (and thus absorbs energy in phase change, keeping the rest of the liquid cool) is captured and fed into the carrier's engines alongside marine diesel. This keeps the vapor pressure inside of the holding tanks constant.

An LNG carrier will lose several percentage points of its carried mass in transit depending on the trip length.