Rio Olympics 2016: While you were sleeping - day 15

Lydia Ko celebrates after sinking a birdie putt on the 18th hole to secure an Olympic silver medal. Photo / Getty

Lydia Ko extended New Zealand's record haul at the Olympics to 17 with a silver medal in the women's golf overnight.

Ko sunk a birdie putt on the final hole to secure the silver medal and finish five shots behind Korea's Inbee Park. If Ko had missed the putt she would have had to go to a playoff for silver and bronze with China's Shanshan Feng who was a further shot back.

Ko had a two-under round of 69 but missed a number of birdie putts which would have been needed to keep up with the superb Park who closed with a five-under 66 to finish the tournament at 16-under.

Ko's silver medal wis New Zealand's ninth of the Olympics, more than double the previous best of four silver medals at the 1992 Barcelona Olympics. Eight of those nine silver medals have been won by females.

It also took New Zealand's total tally to 17, four more than the nation's previous best total of 13. Today was the third straight day New Zealand has won a medal, the second time that has happened at the Rio Olympics.

The women's K4 500m team of Jaimee Lovett, Kayla Imrie, Aimee Fisher and Caitlin Ryan finished fifth in their final, two seconds outside the medals. Hungary took the gold, edging out Germany. Belarus finished with the bronze.

The only other New Zealand athletes competing overnight were the women's triathletes. Andrea Hewitt and Nicky Samuels finished outside of the medals after sitting in the lead bunch off the bike leg.

Hewitt finished in seventh and Samuels in 13th as Gwen Jorgensen gave the US its first Olympic triathlon gold medal. The heavy race favourite crushed the field in the run to finish in a time of 1 hour, 56 minutes and 16 seconds.

Nicola Spirig of Switzerland, who won gold in London four years ago when Jorgensen was bamboozled by a flat tire, crossed 40 seconds later for the silver medal. Vicky Holland outsprinted British teammate Non Stanford to win the bronze.

Later today Nick Willis runs in the 1500m final.