The use of infrared-triggered activity monitors in wildlife science has increased during recent years. In most cases, trail monitors are mounted to stationary objects. However, trail monitors in aquatic environments where change in elevation is necessary, because of varying water levels, curently restricts their use. In our study of Florida Key deer, we needed information on deer activities in areas influenced by tides. We developed an inexpensive device that allowed trail monitors to operate as tides changed. We propose that this device can expand the use of trail monitors to include aquatic environments.