A Lower Mainland man is missing and presumed drowned after a boat trip on the Squamish River over the long weekend.

Squamish RCMP Cpl. Dave Ritchie said the 20-year-old and his brother jumped out of a small boat they were floating in with three others Sunday afternoon.

The brother was able to grab a hold of a tree and was rescued, but the victim never returned to the surface. It is believed he was swept away in the fast-moving water.

Squamish Search and Rescue crews carried out a swift water search by boat and helicopter, but a search was called off late in the day.

"The river currents are very strong and the visibility is at zero due to silt and debris in the water," Ritchie said in a statement.

The victim is a Metro Vancouver resident. His name has not been released.