Calgary firefighters are warning Bow River rafters not to tie boats together after they rescued a woman who became tangled in the ropes.

On Tuesday night, six women in their 20s were floating down the river in three rafts tied together when they got caught in fast-flowing water around the 85th Street bridge, firefighters said.

Five of the women managed to get to shore, but one woman's arm was tangled in the ropes and she couldn't get a foothold.

A fire department boat managed to get close enough to allow rescuers to cut her free, but she suffered minor injuries and hypothermia,firefighters said.

None of the rafters was wearing a life jacket, a must within city limits,thefire department said in a statement.

The department is urging inexperienced rafters to stay off the rivers.

"Both the Bow and the Elbow rivers are still flowing high due to the runoff and demand the respect of those who may venture out on them. Although the weather is warm, the water is still very cold and still dirty due to the runoff," the statement said.