The swimming world is in shock after 400m freestyle world record holder Summer McIntosh bombed out in the heats at the Pan Pacific Championships in California, opening the door for Australia’s Lani Pallister.

As the year's biggest event begins, McIntosh is already firmly at the top of the sport. The question now is how much better can she get.

Australian Lani Pallister edged three-time Olympic gold medallist Summer McIntosh to win the women's 200m freestyle at the Pan Pacific Championships on Wednesday in Irvine,…