For years, the United States and Australia have duked it out for dominance in the Olympic swimming pool. Now, with U.S. legend Michael Phelps retired and Katie Ledecky slipping in some races, it might be Australia’s turn at the top of the podium.The Washington Post’s Ava Wallace speaks with Post reporters Dave Sheinin and Rick Maese about the newest stars in the pool this year and which races not to miss.Subscribe to Ava’s newsletter here. Subscribe to The Washington Post here.Today’s show was produced and mixed by Ted Muldoon. It was edited by Joe Tone.