This paper evaluates Kuipers’ account of functional explanation in biology in view of an example of such an explanation taken from real biology. The example is the explanation of why electric fishes swim backwards (Lannoo and Lannoo 1993). Kuipers’ account depicts the answer to a request for functional explanation as consisting only of statements that articulate a certain kind of consequence. It is argued that such an account fails to do justice to the main insight provided by the example explanation, namely the insight into why backwards swimming is needed by fishes that locate their food by means of an electric radar. The paper sketches an improved account that does justice to this kind of insight. It is argued that this account is consistent with and complementary to Kuipers’ insight that function attributions are established by means of a process of hypothetico-deductive reasoning guided by a heuristic principle.