Tokyo Olympics: Swimming Heats - Caeleb Dressel marks impressive return to the pool, Great Britain dominance - Updates, results, blog

The Swimming Heats on Day 4 of the Tokyo Olympics saw several interesting developments. US swimmers Caeleb Dressel and Regan Smith were impressive during their Heats and all the attention will be concentrated on them again in the upcoming decisive rounds.

Arno Kamminga and Izaac Stubblety-Cook were involved in an interesting battle during their 200m breaststroke Heats and we'll keep an eye on how they perform tomorrow in the Semi-Finals. Men's 800m Freestyle event was introduced to the Olympics for the first time today and Mykhailo Romanchuk set the Olympic Record in that event during the Heats. That record is expected to tumble in the upcoming rounds.

Caeleb Dressel finishes second fastest in Men's 100m Freestyle Heats

Having won the gold with US Men's 4x100m Freestyle Relay team earlier, Caeleb Dressel marked a celebratory return to the pool during the Heats of Men's 100m Freestyle. Still searching for his first individual Olympic gold medal, the World Champion finished second with a time of 47.73, behind Italy's Thomas Ceccon with a time of 47.71. Australia's Kyle Chalmers also finished strongly with 47.77.

Regan Smith and Hali Flickinger involved in action during the Women's 200m Butterfly Heats

Bronze medalists in Women's 100m Backstroke and 400m Individual Medley Regan Smith and Hali Flickinger were both involved during the Heats of Women's 200m Butterfly. Smith finished with a time of 2:08.46, just marginally behind China's Yu Liyan. Hali Flickinger, meanwhile, won her heat with a time of 2:08.31.

There were only 16 competitors in the Heat after Katinka Hosszu pulled out. There wasn't much incentive left for the swimmers and all of them qualified for the semi-finals.

Battle between Arno Kamminga and Izaac Stubblety-Cook defines Men's 200m Breaststroke Heats

Arno Kamminga held on to the lead for much of the distance in Men's 200m Breaststroke. Unfazed by the challenge and the lead that Kamminga had taken, Stubblety-Cook continued to hold back and conserve himself and in the very last moment, he hit top gear to surprise Kamminga. The duo was tied at the top of the results during the Heat with a time of 2:07.37. Finland's Matti Mattson finished third.

Great Britain reign supreme in Men's 4x200m Freestyle Relay Heats

Great Britain were levels above their opposition during the heats of Men's 4x200m Freestyle. They defeated both Australia and United States of America during their own Heat and also beat the time set by Italy and Russian Olympic Committee in Round 1.

Mykhailo Romanchuk sets the first Olympic Record in the newly inducted Men's 800m Freestyle

Round 4 of the Heat was where all the action was during Men's 800m Freestyle which has been inducted into the Olympics for the first time. Ukraine's Mykhailo Romanchuk beat close attention from Germany's Florian Wellbrock and America's Robert Finke to set the first Olympic Record in the event with a time of 7:41.28. Wellbrock and Finke had times of 7:41.77 and 7:42.72 respectively.