The Discovery Center [1] has detailed information on sea kayaking in the waters near Ketchikan [2], including Misty Fiords [3] and a circumnavigation of Revilla Island.
Southeast Sea Kayaks (907/225-1258 or 800/287-1607, www.kayakketchikan.com [4]) leads a variety of kayak trips, including a 2.5-hour paddle along Tongass Narrows ($94) and a 4-hour trip ($159) that includes a boat ride to a quiet cove and the chance to explore by kayak. An all-day trip to Misty Fiords ($559) includes the boat ride over and back, lunch, and four hours of paddling.
Located 13 miles north of town at Knudson Cove, Southeast Exposure (907/225-8829, www.southeastexposure.com [5]) has a range of trips that are especially popular with cruise ship passengers, starting with a $65 paddle to Eagle Island. Bike tours and zip-line adventures are also available.
Both Southeast Sea Kayaks and Southeast Exposure also offer multiday trips to Misty Fiords [3], kayak rentals, and water taxis.
Links:
[1] http://www.moon.com/destinations/alaska/southeast-alaska/ketchikan/sights/downtown-ketchican
[2] http://www.moon.com/destinations/alaska/southeast-alaska/ketchikan
[3] http://www.moon.com/destinations/alaska/southeast-alaska/ketchikan/excursions-ketchikan/misty-fiords-national-monument
[4] http://www.kayakketchikan.com
[5] http://www.southeastexposure.com