Great Britain has secured four of the five relay spots at this summer's Paris Olympics through the World Athletics Relay Championships in the Bahamas.
The women's 4x100m team won the first heat on the first day, while the men's 4x100m quartet and the 4x400m men's and women's teams both placed second in their heats.
The top two teams from each heat advanced to the finals on the second day and also qualified for the Olympics.
The second day's racing will determine lane seeding for the tournament.
The women's 4x100m team of Asha Phillip, Imani-Lara Runsicott, Bianca Williams and Amy Hunt won their fourth heat, setting a season-best time of 42.33 seconds.
They finished second overall on the first day, behind the Americans who won the first heat.
“It was incredible. It was my first time with these three girls,” Hunt said.
“They believe in me, coach me and make sure I’m on that path, which is really great.
“So being able to pick up that baton and cross the line with the biggest smile on my face was one of the most fun races I've ever had.
“We're very, very happy because we came here and did our job and got it done.”
The men's team of Zarnell Hughes, Nethanil Mitchell-Blake, Richard Quilty and Eugene Amo-Dazy ran a season-best time of 38.36 seconds, finishing second in their heats behind France.
The women's 4x400m was defeated by Ireland with Victoria Ofuruogu, Hannah Kelly, Nicole Yeargin and Lina Nielsen running in 3:24.89.
The men's 4x400m team of Matthew Hudson-Smith, Toby Harries, Lea Thompson and Lewis Davey ran a time of 3:02.10, finishing behind Italy in the heat.
The mixed team of Brodie Young, Ama Pipi, Charles Dobson and Laviai Nielsen finished third in their heats behind winners Ireland and Belgium.
If he can finish in the top two in his heat on the second day, he still has a chance to secure a spot in Paris.
One of the highlights of the first day was Italy, which included Olympic 100m champion Marcel Jacobs, as well as the United States in the men's 4x100m, and 100m world champion Noah Lyles.
Jacobs ran the second leg for his team, with Lyles anchoring the American quartet as the Americans won with a world-leading time of 37.49 seconds, with Italy second in 38.14 seconds.