Wikipedia
Hauling-out is the behaviour associated with pinnipeds ( true seals, sea lions, fur seals and walruses), of temporarily leaving the water between periods of foraging activity for sites on land or ice. Hauling-out is necessary in seals for mating (with the exception of the Baikal seal) and giving birth (though a distinction is generally made between reproductive aggregations, termed " rookeries", and non-reproductive aggregations, termed "haul-outs"). Other benefits of hauling-out may include predator avoidance, thermal regulation, social activity, parasite reduction and rest.
There is much variety in haul-out patterns among different seal species. Haul-out sites may be segregated by age and sex within the same species. Many species of pinniped have only a few localized rookeries where they breed, but periodically occupy hundreds of haul-out sites throughout the range. For example, the Australian fur seals breed on only nine islands in Bass Strait but also occupy up to 50 haul-out sites in south-east Australian waters, and Steller sea lions have around 50 rookeries throughout their range, but several hundred haul-out sites.