Few leave Bocas del Toro [1] without taking at least one boat tour [2], which is by far the most popular outdoor activity. These tours usually include snorkeling [3], but those not interested in that can just splash around in the water or sun themselves on the boat or the beach during snorkeling stops.
Scuba diving [3] and surfing [4] are also popular, and as tourism takes off in Bocas more and more outfitters with more and more toys are showing up. Though of interest to just a minority of visitors, forest hikes [5] and camping are also possible.
Nearly all the guides and outfitters in the archipelago are in Bocas town, and most of these are found along Calle 3.
Links:
[1] http://www.moon.com/destinations/panama/bocas-del-toro
[2] http://www.moon.com/destinations/panama/bocas-del-toro/isla-colon/recreation/boat-tours
[3] http://www.moon.com/destinations/panama/bocas-del-toro/isla-colon/recreation/diving-and-snorkeling
[4] http://www.moon.com/destinations/panama/bocas-del-toro/isla-colon/recreation/surfing
[5] http://www.moon.com/destinations/panama/bocas-del-toro/isla-colon/recreation/hiking