The impact of devices attached to animals remains a challenge in telemetry studies of dolphins. It was hypothesized that the hydrodynamic design of a tag could provide stable attachment to the dorsal fin by means of resultant hydrodynamic force appearing when a dolphin is swimming. To verify this hypothesis the computer fluid dynamics (CFD) study of tag performance was carried out. A virtual model presenting authentic geometry of a dolphin with tag attached to the dorsal fin was constructed. The same model without tag was used as a reference object to calculate tag impact as regards drag, lift, and moments coefficients. Flow around the models was simulated for the range of velocities as well as the ranges of pitch and yaw angles. It was shown that in 33 of 35 CFD scenarios the streamlined shape of a tag generates the lift force that facilitates keeping a tag attached to the fin. Throughout the set of calculations the tag-associated drag coefficient does not exceed 4%, which indicates low impact. Data obtained present a baseline for the further development of non-invasive dolphin telemetry tags.