The incident took place between Lock 11 and 12, near Ashtown at about 7.25pm on Friday.
The video shows the woman telling a group of young people that they should not be racially abusive before being pushed into the water.
It was then posted on the video sharing platform TikTok before being shared on other social media platforms.
The original video was subsequently deleted from TikTok, along with the associated account.
Gardaí are asking anyone who was in the area and may have information relating to the incident to contact them at Finglas Garda Station.
The Irish Network Against Racism (INAR) say the incident shows that racism exists in Ireland.
Director of INAR, Shane O'Curry, says we must acknowledge that racism is an issue here.
"It is very important to the wider community, including ethnic minority communities, that we face up to the fact that this is a racist incident and that we have racism in our society."
