 Acoustic telemetry has been used with great success to quantify the movements of marine fishes in open habitats, however research has begun to focus on patterns of movement and habitat usage within more structurally complex habitats. To date, there has been no detailed assessment of the performance of acoustic telemetry within seagrass, which forms a crucial nursery and foraging habitat for many fish species globally. Information on the detection range of acoustic receivers within seagrass is essential to guide receiver array design, particularly positioning systems. Here, we compare detection ranges for transmitters (Vemco V7) within and above the seagrass to determine impacts on the performance of a Vemco Positioning System (VPS). We also investigate the influence of environmental conditions (i.e. wind, time of day, background noise, atmospheric pressure and depth) on detection probability.