I will discuss two problems inspired by fish behavior. First, I will show that zebrafish generally escape in a direction orthogonal to the predator’s heading and that when operating within the biomechanical constraints of the escape response, this strategy provides the best predictions of prey behavior among all alternatives. Second, I will show that flow interactions among flapping swimmers lead to the emergence of dynamic formations with versatile spatial patterns, ranging from cooperative « phalanx » patterns that favor egalitarian distribution of energy savings among group members to greedy « inline » patterns where few members get maximal benefit, leaving trailing swimmers with diminished opportunities for maintaining group coherence and gaining energetic benefits.