"We usually have 112 or so women, so we know this is our best year ever. We think it may also be a record number of men," says race director Brian Mongey.
Starting together are the two favourites for the women's title.
Julieann Galloway of NAC Masters is a Texan studying in Ireland who narrowly failed to make the US Olympic swim team for Athens.
At the Dun Laoghaire Harbour swim a few weeks ago, she proved fastest of the women with a time of 29 minutes 5 seconds for the 2.2km distance and she is booked in for an English Channel attempt next summer.
Taking her on is Dublin fire-fighter Rachel Lee, who has regularly posted the fastest time on the Liffey and is a past winner in Dun Laoghaire.
Whether either woman will win the race is in the hands of handicapper Joe Brown who has refined his approach to the job over the past 20 years. "Joe will pick 15 or 16 and give them a chance," says Brian Mongey.
Women often post faster times than men on the Liffey -- starting after the men, they can take full advantage of the high tide sweeping them down to Dublin Bay.
"High tide in the Liffey can vary by a metre, making it very difficult to judge the flow of the water. That's why times can vary so much from year to year, compared to the Dun Laoghaire harbour swim," says Mongey.
Last into the water of the men, over five minutes behind the first starters, will be Shane Drumm of ESB, who is expected to record the fastest time of the day.
To qualify, swimmers must have swum at least four races in the annual Leinster Sea Swimming League. Wetsuits are not allowed and although the Liffey is a lot cleaner than it used to be, drinking it is not recommended. "The Liffey is a lot cleaner these days -- I remember when I started about 20 years ago, I would come out of the water looking like a coalminer," says Mongey.