Used to avoid the scientific and medical implications, whose truths may be too confrontational.
Often used to piggyback off the sympathy from similar terms such as "People of color", a legitimately discriminated group.
Doctor: "Your current weight qualifies you as 'obese'. We can help you return to a healthy weight."
Patient: "That won't benecessary because I'm not obese, I'm 'people of size'."
girl: how big is your cock?
guy: 6 inches
girl: ok, i'll go with that
guy: you need to understand that it ain't all about the size of the boat, it's about the motion in the ocean girl: yeah, yeah whatever.
The "Boat" refers to the size of a penis. The expression is used when a person says when he/she talks about penis size. This statement is usually countered with the motion of the ocean.