We use a leaf plug on top of the piece of bamboo that is steaming the fish. This both retains the water (steam) that is trying to escape and this particular leaf adds a bit of flavor to the fish. Water soluble nutrients would escape with the steam, so in a true survival situation it makes sense to drink some of the water that was used in cooking the fish.
|Cooking fish in bamboo|
|The finished product is a perfectly steamed fish|