A FORRT replication study testing whether the daily geolocations of juvenile white sharks (Carcharodon carcharias) released by O'Sullivan et al. (2022), computed by the proprietary GPE3 light-plus-SST model, can be reproduced with a fully open method. It re-derives positions with pangeo-fish — a HEALPix-NESTED hidden Markov model matching tag temperature-at-depth against the GLORYS12V1 ocean reanalysis — and compares both against co-deployed Argos SPOT fixes as an independent referee. In a minimal temperature-only configuration the open method is materially less accurate than GPE3 (median 276 km vs 54 km great-circle error across four tags), qualifying the reproducibility of the released geolocations with open tooling.