A remarkable first morning at the Swim Ireland National Team Trials at the NAC in Dublin saw both Larne's Daniel Wiffen and Tennessee-based Mona McSharry dip under the Olympic qualifying time for the men's 800m freestyle and the women's 100m breaststroke.

Wiffen swam a time of seven minutes 52.68 seconds in the 800m freestyle, now part of the Tokyo Olympic programme, with the 20-year-old smashing not only Andrew Meegan's 2013 Irish record by almost 13 seconds, but also dipping under the FINA A consideration time for the Games by over 1.5 seconds.

A delighted Wiffen said: "It's probably the most nervous competition I've ever been to. I only managed to eat cereal for breakfast. I was thinking about it all day.

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"I knew I had to be in and around 3:55 out on the 400m free, so I wanted to be quite comfortable out. I kinda knew I went out the right time and towards the end I had a cheeky look at the clock on the last 50 to see where I was. I just got my head down then to get that time.

"It’s unbelievable – 19 and going to the Olympics."

McSharry, the former junior world champion, also set a new Irish record and went under the Olympic qualifying time for her main event, the 100m breaststroke, winning her heat in 1:06.97, 0.1 of a second under the qualifying mark.

McSharry swam even faster in the semi-finals, registering a time of 1:06.29 to set her second Irish record of the day, a time that ranks her seventh on the current world rankings.

McSharry and Wiffen now join Shane Ryan and Darragh Greene, who have already posted times to qualify for the Games in July, and will now go forward for ratification from the Olympic Federation of Ireland.

Greene also set a new Irish record in the 100m breaststroke in winning his heat in 59.86, his second time to go under the Olympic qualifying time for the event.

Ryan eased through his heat of the 100m backstroke and will hope to bring Conor Ferguson through to a qualifying time in Wednesday night's final.

There was disappointment for both Brendan Hyland and Jack McMillan in the 200m butterfly and 200m freestyle.

Both won their semi-finals but were marginally outside the Olympic qualifying standard ahead of Wednesday night's finals.

There are also a number of Irish Paralympians taking part during the five-day meet at the NAC.

Paralympic Games slots are awarded to nations based on the world ranking positions. Ireland have secured three female places and one male spot so far.

Swimmers are competing against one another for these slots. Ireland hope to secure another slot in the next round for the males as they have two males qualified.

Swim Ireland cannot pre-select competitors as swimmers are competing against one another.