[mapmaker77]

I’m not a chemist but at what point does methane gas freeze and thaw?

[Greysard]

at what point does methane gas freeze and thaw?

Here is the explanation of these crystals. Methane gas freezes at very low (cryogenic) temperatures, but "methane ice" can be solid up to +18C under high pressure (which is present down there.)

[TaMoDee]

Melting point at STP (Standard, Temperature, Pressure)
is -297F. Hence the use of CH4 as “natural gas”.
The pressure at 5000 ft of water is 2165 psi, probably higher with the sea water column due to the increase of SpGr over “regular” water. I’ll have to figure out what the melting point is at that pressure but it is very low.