A terrific session of swimming took place on the sixth session of prelims at the Olympic Games Tokyo 2020. Caeleb Dressel tied an Olympic record, Katie Ledecky and Katie Grimes finished 1-2 out of all semifinalists in the 800-meter freestyle and Tom Shields flipped a 20-minute double to qualify for semifinals in the individual 100m butterfly and help the U.S. to a second-place finish in the inaugural Olympic 4x100m medley relay.

More from day six prelims:

Women’s 800m freestyle
• Both U.S. swimmers advance to the final. Ledecky in top speed with an 8:16.67 and Grimes in second seed with an 8:17.05.
• Ledecky and Grimes swum in the same heat, Ledecky holding first from start-to-finish while Grimes held second until the 500-meter mark, when two other swimmers joined her and alternated sports two-through-four for the remainder of the race before the American touched in second.
• Ledecky is attempting to become the third-woman to ever three-peat Olympic gold medals in a single event.
• Grimes' final three 50-meter splits were 31.13, 30.80 and 29.77 to climb from fourth to second in the last three lengths.
• Seeds two-through-four heading into tomorrow’s final are separated by three tenths.
• Grimes cut three seconds from her personal best, which she previously set at the U.S. Olympic Team Trials – Swimming. She has now shaved 20 seconds off her pre-Trials personal best.

Men’s 100m butterfly
• Both U.S. swimmers advance to semifinals. Dressel will be top seed in 50.39 followed by Shields as the 12th seed in 51.57.
• Caeleb Dressel tied the Olympic record.
• Dressel’s 50.39 is tied for the 16th-best swim of all time. He now owns 11 of the top-20 swims in the event’s history.
• Shields’ time was a hundredth faster than his prelim swim in the event at the 2016 Rio Olympics.
• The semifinal field of 16 is separated by just 1.35 seconds.

Women’s 200m backstroke
• Both U.S. swimmers advance to semifinals. Rhyan White tied for second seed with a 2:08.23 while Phoebe Bacon will enter as the fourth seed with a 2:08.30.
• U.S. duo competed in the same heat and posted a 1-2 finish.
• White was 1:02.78 at the 100-meter mark, Bacon was 1:02.71.

Mixed 4x100m Medley Relay
• U.S. relay team advances to final as second seed with a 3:41.02.
• Relay team consisted of Regan Smith in backstroke (57.64), Andrew Wilson in the breaststroke (59.09), Shields in the butterfly (50.87) and Abbey Weitzeil in the freestyle (53.42).
• Smith’s backstroke split was more than four tenths faster than her bronze-medal winning swim in the individual event.
• U.S. finished second in their heat.
• Event is making its Olympic debut – U.S. won silver in the event at the 2019 FINA World Championships with a lineup of Ryan Murphy, Lilly King, Caeleb Dressel and Simone Manuel.
• Tom Shields swum his butterfly leg of the relay roughly 20 minutes after swimming the individual event. At age 30, Shields is the oldest male on this year’s U.S. Olympic Swimming Team.

Action from Tokyo resumes at 10:30 a.m. / 7:30 p.m. ET with finals of the women’s 200m breaststroke, men’s 200m backstroke, women’s 100m freestyle and men’s 200m I.M., as well as semifinals of the men’s 100m butterfly and women’s 200m backstroke.