The qualitative resemblance between terrestrial and submarine branched valley networks has led to speculation that common underlying processes control their formation. However, quantitative comparisons have been impeded by methodological limitations and coarse resolution in marine systems. We analyze channel concavity and steepness indices of 23 terrestrial and 29 submarine catchments to determine whether their profile morphologies are distinct. Statistical comparisons of these quantities demonstrate that concavity indices in submarine systems are, in general, lower than in subaerial systems, and that submarine tributaries are steeper than their associated mainstem. These differences may reflect distinct drainage formation mechanisms and dynamics of submarine sediment gravity flows as compared to overland flow processes.