Looks like Nel's inspecting a vent in a mid-ocean rift, and is a bit concerned about what he's seeing. An unexpected occurrence?
As always, wonderful use of detail & color. The lighting of the crystals and magma effectively build the sense of being underwater, and the latter in particular looks realistic: it has that characteristic shimmer of superheated water rising.
Nel's beard is floating a bit, but emphasizing that a little more might strengthen the underwater feel & reinforce what he's doing. If he just swum around the ridge and stuck his head over to look at the vent, then his beard would be swept back from the current, and also spread out from the eddies that would form around his head.