Diving abilities of fledging Brown Boobies (Sula leucogaster) were characterized during the transition to independence period, and potential inter-sex differences (females are larger than males) were evaluated. Mean and maximum diving depths and mean dive duration increased gradually following the fledglings' first flights. The diving rate and the proportion of active dives (U type) increased notably between days 21 and 25 after first flight. However, maximum dive duration was not influenced by time since first flight, and none of the dive variables evaluated was influenced by sex. In Brown Boobies, acquisition of diving abilities by juveniles is a gradual process, and this can be an important driver of their extended post-fledging parental care.