In applying foraging theory to cryptic predators like many snakes, one of the most difficult variables to measure is effort spent in foraging. We estimated foraging effort from time invested in foraging using records for habitat use accumulated over a period of three years for 50 radio-tracked adult watersnakes (Nerodia sipedon). Because watersnakes eat predominantly aquatic prey, and limited prey records for the population studied were all fish, time spent foraging was estimated from the number of records in which snakes were found in water compared to the total number of records. Based on the data collected, this population of watersnakes devoted 1.43–2.38% of its time to foraging. Although the data do not permit allocation of foraging effort for most snakes to specific times, combining all relocation data suggests that adult watersnakes in this population forage infrequently. Opportunistic records of stomach contents regurgitated by captured snakes of all sizes suggest that these watersnakes find fish prey by active foraging and that the adult population benefits from periodic exploitation of dead or dying large fish (trout) following stocking.