The first of Sunday's swimming finals in Tokyo delivered an absolute nail-biter as the top four swimmers in the women's 100m butterfly all finished within 0.14 seconds of each other.

Canada's Maggie MacNeil got her fingertips on the wall first in 55.59, which ended up as the gold medal-winning time — just. China's Zhang Yufei finished .05 behind for silver. 

The margins were tightest where tightest in the fight for bronze. Australia's Emma McKeon got in one one-hundredth ahead of American Torri Huske to round out the podium.

Sarah Sjostrom, the Rio 2016 gold medalist from Sweden, finished seventh.

MacNeil, the gold medalist, competes for the University of Michigan and is a two-time NCAA champion.