This is a perfect kayaking trip or camping trip soup, for several reasons: first, it requires just one pot/stove burner; second, it requires few ingredients; third, refrigeration needs are minimal; and fourth, it's so good that you won't have leftovers to mess with!
You can either purchase oysters and shuck them at your site (if you're kayaking somewhere where it would be a crime to NOT buy local oysters, like Tomales Bay or some other oyster-growing region), or, if shucking oysters is not your thing (some day I'll share my oyster-shucking-near-death-experience), you may purchase them from a fish monger in a jar. Considering the work it takes to shuck oysters, and since you're going to eat them poached rather than raw this time around, it actually makes sense to buy them already shucked.
This entire soup may be made at your campsite, although chopping the onions, fennel, and peppers at home makes life easier. The corn should stay frozen, as it will help keep your oysters cold, too. However, if you'd prefer, go ahead and make the entire soup at home -- it reheats very well.
This is a perfect soup for folks who don't think they like oysters. If you really have die-hard oyster-haters, substitute shrimp. Either way, this soup is a hearty winner.