The objective of this paper is to obtain pixel-accurate reconstructions of white shark fins given automatically generated coarse pre-segmentations. Reconstruction performance is compared for affinity matting, colour matting and GrabCut against expert annotated ground truth for a test-set of 120 fin images taken in the wild. For the present domain, we find affinity matting able to most accurately recover fine shape details, whilst being robust to wide baseline trimap initialisations as needed to reconstruct prominent notches on the fin edge.