At high altitudes, Neptune’s atmosphere is 80% hydrogen and 19% helium. A trace amount of methane is also present. Prominent absorption bands of methane exist at wavelengths above 600 nm, in the red and infrared portion of the spectrum. This absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue.
We advise you to bring your own oxygen supply and take a first dive in superionic water with our specially trained diving-crew.