Dive data were obtained from telemetry studies performed on ten harbour seals (Phoca vitulina) and twelve grey seals (Halichoerus grypus) captured in the Baie de Somme, France, in 2008 and 2012, respectively. These seal individuals were fitted with Fastloc GPS/GSM tags, developed by the Sea Mammal Research Unit (University of StAndrews, UK). These tags include a Fastloc™ GPS, a GSM modem (for data transmission), and wet-dry, pressure and temperature sensors, as well a microprocessor (for on-board data processing) (McConnell et al., 2004). A dive event was registered by the tag when the seal reached depths exceeding 1.5 m, and different parameters were thus measured: start date and time, maximum depth, dive duration, post-dive surface duration, the “percent area” (to identify dive shape, cf. TAD index by Fedak et al., 2001), and nine intermediate depth points (each 10% of the dive duration). GPS locations were obtained (around every 20 minutes) when the seal was at the surface at sea, and the location of each dive data was therefore spatially interpolated from these GPS locations. GPS data are already available on http://seamap.env.duke.edu/dataset/2030 for harbour seals and on http://seamap.env.duke.edu/dataset/2026 for grey seals seals. Dive data can provide essential information on the behaviour of seals, including foraging, and can therefore be used to identify foraging areas (as already done on part of these data, cf. Planque et al., 2020). For information, the δ13C and δ15N stable isotopes were measured along the whiskers of almost all of these seal individuals, and the data are already available on SEANOE (https://doi.org/10.17882/76528).