We booked a Sea Kayaking adventure to Tatoosh islands through Celebrity cruises but it was though SoutheastExposure. It was easily the best land excursion we booked. It was better than the hellicopter ride to the glaciers in Juneau and the train ride in Skagway. There were 12 people and 2 guides and like it says, you take 2 person Kayaks out around the island. The guides were awesome and we saw seals, minks on the shore, and on the way back to the dock we came accross 2 humpback whales feeding in the bay. They stopped the boat for twenty minutes so we could watch and take pictures. I would recommend booking this through the cruiseline because it did not start until 2PM and we did not get back to the boat until 7PM. They will let you stay and play all day if you want.
The kayaks are very stable. You would have to work awfully hard to tip one over.
The tatoosh island kayaking is a very nice excursion. It was raining when we went, so you do get very wet, but they provide splash suits which keep you pretty dry.
We took disposable waterproof cameras. The paddles drip saltwater on your skirt, so your camera equipment will get wet from salt water no matter what you do. A disposable waterproof can hang around your arm with no worries, but also no video. Oh well. Can't have it all.