1920: The US team training at the deck of "Princess Matoika"

The US Water Polo players for Antwerp 1920 Olympics, coming from all over the country, practiced for the first time all together, under their coach the legendary Otto Wahle, in a 12' by 9' swimming tank specially constructed on the deck of the Princess Matoika, the ship that was carrying the United States Olympic team to Antwerp.
Source: A History of USA Water Polo in the Olympic Games.