Thick black oil hung in the water and stained the bases of the roseau cane at Pass a L’Outre, a shrinking patch of Louisiana’s fragile wetlands where crude from the BP spill first hit land and began seeping deep into the fragile marshes. Three rows of boom laid in front of the marshes appeared to serve little purpose, and if anything were corralling the oil up against the wetlands’ plants, not keeping it away.