One person was believed to be in the vehicle.
Dublin Fire Brigade and emergency services attended a water rescue incident at Howth pier on Wednesday evening.
According to RTÉ, a car entered the water at Howth Pier, with one person believed to be in the vehicle.
The response to the incident involved a coastguard helicopter, an RNLI lifeboat and an Garda Síochána, with members of its Water Unit travelling to the scene.
Dublin Fire Brigade posted about the incident on Twitter, saying: "We're currently attending a water rescue incident in #Howth as part of a multi-agency response involving @IrishCoastGuard @RNLI @howthcoastguard & firefighters from Kilbarrack, North Strand with advanced paramedics."
https://twitter.com/DubFireBrigade/status/956222193515589633
Divers have since entered the water and attempts are being made to raise the vehicle.
https://twitter.com/padraig_reilly/status/956222486013792256