The twin lens reflex camera is obviously a Rollieflex Rolleiflex. The other camera appears to be a Leica with a 135mm Elmar lens and a lens hood to shade it from the sun.

From 1922 to 1938 Harold "Mike" Vanderbilt won six King’s Cups and five Astor Cups and steered three J-Class sloops to America’s Cup wins in the 1930s. I found references to him and boats named Enterprise, Rainbow, Ranger, and the Versatile shown here. How many boats did he go through in the course of his life?

Mr. Vanderbilt is giving instructions to the Matt Damon cabin boy to make certain that all the guests (including the aforementioned anatomy and physiology student) have what they need -- drinks freshened, cigarettes lit, etc. He might even be giving specific mixing instructions for his own "Stirling Punch". Or perhaps he's retelling some yarn about his regatta days on the Harvard eight and how on this one rainy windswept occasion, they edged out Yale's eight by a nose because they'd trained in the unpredictable waters of the Charles River basin. All in good fun, old sport!