SEATTLE – The Shell Oil Arctic drilling rig Polar Pioneer headed out of Seattle Monday on its way to Alaska, but not before an attempted blockade by protesters in kayaks.

The Coast Guard said 24 protesters were detained for violating the safety zone. One of them was Seattle City Councilman Mike O'Brien. Seattle City Hall says O'Brien was booked and fined $250. He was later released.

The Polar Pioneer undocked from Terminal 5 at 6 a.m., pulled by tug boats.

Protesters sent out an alert Sunday night to supporters to block the departure.

After slowly moving out of port in an effort to avoid collisions with the kayaks, the Polar Pioneer and tugs were cruising through Puget Sound by 7:30 a.m.

The mission of protesters from the start has been to pressure officials to end dependency on oil and stopping Arctic Ocean drilling. They say every minute they cause the Polar Pioneer to be delayed is another minute Pres. Barack Obama can decide to reverse his decision to allow drilling in Alaska.

In recent weeks, protesters have used kayaks to get their message across. They also have blocked streets leading to Terminal 5 in the hopes of preventing prep work on the rig. That has led to standoffs with police and some arrests.

The rig arrived in Seattle May 14.