It proved a magnificent swim for Boyle who was a touch away from a negative split to take nearly five seconds off the New Zealand record she set at the world championship trials.
In that performance she took nearly three seconds off her previous best to knock off a 19-year-old national record.
Her coach Mark Regan said he had been concerned with the big workload on Boyle at the championships, after swimming the 200m, 400, and 2x200m relay on top of the 800m.
"She has worked so hard and done a tremendous amount of work. Today showed the benefit of that and how she will get a welcome day off and the challenge will be to get her weary body back up for one more big swim tomorrow night in the final,'' Regan said.
British Olympic champion Rebecca Adlington topped qualifiers in 8min 22.27sec ahead of the defending champion Lotte Friis of Denmark, who swam under Regan when he was national coach in Denmark.
Meanwhile Ingram showed her experience to move through to tonight's semifinals in the women's 200m backstroke.
Ingram, fifth in this event at last year's Pan Pacific Games final and in excellent form in the recent US campaign, clocked a solid 2min 10.59sec to be 14th fastest in heats.
She has swum a series of times in the 2:10 range at key lead-up events at Santa Clara and Mission Viejo as well as the trials in Auckland to suggest the 26-year-old has more in the tank for a major push in tonight's semifinals.
Ingram will likely need to better her national record of 2min 09.13sec, set in the suited days, if she is to advance to tomorrow's final.
It was not such good news for Christchurch 16 year old Sophia Batchelor who struggled to find her form on the world championship stage, clocking 2min 17.06sec, well below her best, and will not advance.
Day 5 heats, New Zealand results:
Women 200m backstroke: Melissa Ingram 2:10.59, 14; Sophia Batchelor 2:17.06, 32.
Women 800m freestyle: Rebecca Adlington (GBR) 8:22.27, 1; Lotte Friis (DEN) 8:23.07, 2; Chloe Sutton (USA) 8:27.72, 3. Also: Lauren Boyle 8:28.50, 7 (NZ record).
- NZPA
