Scott Doney lectures on how gases move between the atmosphere and the ocean, part of MIT's 12.742 Marine Chemistry (Fall 2006). He separates the thermodynamic controls, mainly solubility, from the kinetic controls that govern how fast a gas actually crosses the air-sea interface. The session works through the physical chemistry of gas solubility in seawater, the boundary-layer models used to describe transfer velocity, and the environmental factors, wind speed and sea state among them, that speed up or slow down exchange. Doney ties the mechanics back to real oceanographic problems, including how these transfer processes control the ocean's uptake of gases like carbon dioxide and oxygen. At 78 minutes, this is a full graduate-level session with worked physical reasoning rather than a survey, aimed at students who already have some chemistry and physics background.