Sentence:  Of the nation 's eight million pleasure-boat owners a sizable number have learned that late autumn is one of the loveliest seasons to <WSD>be</WSD> afloat - at least in that broad balmy region that lies below America 's belt line . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)