It’s the red line on the television screen that indicates a world record time, and Team USA saw plenty of it on the fifth day of swimming at Rod Laver Arena in Melbourne. The Americans set three world records to bring the team’s meet total to eight. On Day 5, Michael Phelps (Baltimore, Md.) lowered his own mark in the 200m individual medley, Leila Vaziri (Coral Springs, Fla.) matched the world record she set in the 50m backstroke in last night’s semifinal, and the women’s 800m freestyle relay of Natalie Coughlin (Vallejo, Calif.), Dana Vollmer (Granbury, Texas), Lacey Nymeyer (Tucson, Ariz.) and Katie Hoff (Towson, Md.) shattered the world record from lane eight.

Coughlin put the biggest dent on the record books Thursday, setting an American record in the 100m free semifinal, then returning later in the evening to set the American record in the 200m free as the lead-off for the world-record setting 800m freestyle relay.

Phelps kicked off the evening finals by edging teammate Ryan Lochte (Daytona Beach, Fla.) in the 200m IM. Both swimmers were under world-record pace at the 150, but it was Phelps who pulled out the victory for his fourth gold medal and third world record of the meet. Phelps’ time of 1:54.98 was almost a second faster than his previous record of 1:55.84, set at last year’s Pan Pacific Championships. Lochte was just over a second behind Phelps, touching in 1:56.19 for the silver medal. Hungary’s Laszlo Cseh earned the bronze with a time of 1:56.92.

The women’s 800m free relay was the eighth seed coming into the final, but the lane eight placement didn’t seem to make much of a difference for the Americans. Coughlin jumpstarted the relay with a lead-off leg of 1:56.43 to break the American record in the 200m free set by Hoff last night. The remaining three maintained and built on Coughlin’s substantial lead to finish in 7:50.09, more than seven-tenths of a second faster than the previous world record of 7:50.82, set by Germany at the 2006 European Championships. Germany was almost four seconds behind for the silver medal (7:53.82), and France claimed the bronze (7:55.96).

Coughlin earned the first American record in the semifinal of the 100m free, winning her heat in 53.40. Coughlin will be the top seed headed into Friday’s final, with Australia’s Libby Lenton and world-record holder Britta Steffen of Germany rounding out the top three. American Amanda Weir (Lawrenceville, Ga.) did not make it to finals, finishing in 15th place with a time of 55.47.

Vaziri equalled her own world record of 28.16 in the 50m back, which she set in last night’s semifinal. Aliaksandra Herasimenia of Belarus was the silver medalist in 28.46, and Australia’s Tayliah Zimmer won bronze with a time of 28.50.

Kim Vandenberg (Moraga, Calif.) earned the fifth U.S. medal of the evening, capturing silver in the 200m butterfly with a time of 2:06.71. Vandenberg was just three-tenths behind gold medalist Jessicah Schipper of Australia, who won the race in 2:06.39. Poland’s Otylia Jedrzejczak – the former world champion – took home the bronze medal (2:06.90). This is Vandenberg’s first world championship medal.

In other finals action, Jason Lezak (Irvine, Calif.) took fifth in a stacked 100m free field. Two men won gold – Italy’s Filippo Magnini and Canada’s Brent Hayden – as the pair touched the wall in 48.43. Eamon Sullivan of Australia was just four-hundredths behind them in the bronze-medal position.

Three other semifinal races were contested Thursday night, as all five Americans advanced to tomorrow evening’s finals. Lochte returned after claiming his silver medal to take the top seed in the men’s 200m back, finishing four-tenths ahead of U.S. teammate and world record-holder Aaron Peirsol (Irvine, Calif.). Lochte touched in 1:55.99, while Peirsol finished in 1:56.39. Austria’s Markus Rogan, who swam for Stanford, is the third seed (1:56.62).

Two Washington natives, Megan Jendrick (Puyallup, Wash.) and Tara Kirk (Bremerton, Wash.), advanced to the finals of the women’s 200m breaststroke. Jendrick is the fourth seed (2:26.14), while Kirk squeezed into the final as the seventh seed (2:27.41). World record-holder Leisel Jones of Australia is the top seed, posting a 2:23.75.

Eric Shanteau (Atlanta, Ga.) is the lone U.S. representative in the men’s 200m breast, as world record-holder Brendan Hansen had to withdraw from the morning preliminaries due to illness. Shanteau is the fifth seed with a time of 2:11.54, more than a second behind top seed Kosuke Kitajima of Japan (2:10.30).

Preliminary heats in six events will be contested on Friday morning, including: women’s and men’s 50m free, women’s 800m free, men’s 100m fly, women’s 200m back and men’s 800m free relay. Footage of the world and American record performances, as well as all the action from tonight’s finals, is available on-demand at wcsn.com.