Tracking data of 18 harbour seals and 9 grey seals were obtained from the deployment of Fastloc GPS/GSM tags developed by the Sea Mammal Research Unit Instrumentation Group (UK). Full tag description is available at: http://www.smru.st-andrews.ac.uk/Instrumentation/GPSPhoneTag/. The tags include a wet-dry sensor from which haulout events are recorded, a pressure sensor providing detailed dive data, as well as a Fastloc GPS recording irregular locations when the seal is not underwater. Data is stored onboard and transmitted via the GSM network when the seal is in the reception range. The data provided here are the individual GPS locations, dive parameters and haulouts of the seals fitted with these tags.