https://www.abebooks.com/Motor-Yacht-Ca ... id=1&pid=1
The yacht itself was quite large and luxurious:
His Master's Voice Was Eldridge R Johnson, by E.R. Fenmore Johnson, https://worldradiohistory.com/BOOKSHELF ... n-1974.pdfThe CAROLINE'required a crew of forty-two men, including the master and his mates. In addition to that there was a staff of eight cooks and stewards and a radio operator. This came to a total of fifty-one persons, not counting a maid and a valet who were -quartered in the passengers' section of the vessel and were supposed to be brought aboard by the owner and his wife
Unfortunately for Johnson, Senior, this cruise would be the last he would take.. He fell into a deep "melancholia" soon afterward, that lasted until the end of his days.
William Stephenson was not a part of the Smithsonian expedition, but weassociate him with them, as he, supposedly, hosted or attended a dinner party for the crew when the ship over-nighted in port at Hamilton, Bermuda. However, there is no evidence for such a stop nor such an encounter in Fenmore Johnson's account of the cruise, which begins on page 163 of the above linked .pdf.
On another Caroline related note, I have been told, that the impetus for the alliance was born in France between the wars. Those who had seen the horror of the first World War and pledged themselves to do all in their power to prevent another.
I also seem to remember being told, or reading, that the group came about through the actions of women, but this seemed improbable to me, given women's lack of power and influence at the time. As this is third or fourth hand information, I am just posting it here, for the record and in the event that more information should come to light.