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Abstract Background Conserving marine predators is tantamount to maintaining functional marine ecosystems. Though intensively studied in other regions, little is known about at-sea movements and diving behaviors of a recovering population of grey seals ( Halichoerus grypus atlantica ) inhabiting northeastern United States continental shelf waters. Young-of-year grey seals may be particularly vulnerable to threats due to a lack of parental care postweaning. There is a need to establish baseline knowledge of at-sea behaviors in the face of large-scale ocean industrialization. We deployed 63 satellite relay data loggers on young-of-year grey seals to investigate postweaning at-sea movements and dive behaviors prior to the installation of offshore wind turbines. Results Young-of-year grey seals dispersed widely across the continental shelf waters. Collective utilization distributions of seals overlapped with offshore wind planning areas in the winter and spring months, and overlap was lowest in the summer when the seals dispersed northeastward. Maximum diving depth and duration increased in the first two months of nutritional independence and stabilized by April. Dives were classified as being either benthic or pelagic depending on dive depth relative to bathymetry. Seals conducted more benthic diving in the spring and this coincided spatiotemporally with habitat and phenology of an important prey species. Following a diel trend, benthic diving peaked during daylight hours, while pelagic diving occurred more frequently at night. Benthic dives occurred more frequently than pelagic dives in sandy shoals and banks. Furthermore, seals conducted more benthic than pelagic dives in wind energy planning areas. Conclusions Ours is the first comprehensive study on the horizontal movement and diving behaviors in the U.S. population of grey seals, contributing knowledge on the at-sea habits of a vulnerable demographic in relation to other anthropogenic uses of the marine environment. This information will serve as valuable input to conservation management and mitigation plans, and it contributes necessary regional context to the broader understanding of grey seal ontogeny across the North Atlantic. Furthermore, these results provide important baseline information for future comparative analyses of grey seal behavior as offshore wind development expands in scope in this region.