Small-and-coastal-form Bryde's whales (Balaenoptera edeni edeni) are known to inhabit coastal and continental shelf waters. However, little is known on their ethological activities, especially underwater behaviours. Here, we deployed a suction cup tag on a small-and-coastal-form Bryde's whale to study its ethological activities in Dapeng Bay, a coastal water of Shenzhen off the east Pearl River Estuary, China. The whale was tagged for 6 hours in total and displayed a head-lifting feeding behaviour 77 times during two tag deployments. The swim speed, dive duration and depth and bottom duration were collected by the tag to describe detailed information on dive profiles. The rate of feeding behaviours was observed decreasing with the presence of anthropogenic whale-approaching (AWA) boat activities occurring close (within 300 m) to the animal. Our study, for the first time, investigated behaviours of Bryde's whales using suction cup tagging in Chinese waters. The results reveal the dive and feeding patterns of a small-and-coastal-form Bryde's whale with short-term monitoring and provide a fundamental advancement in the knowledge of both the diving behaviour and the behavioural response of this subspecies to human activities. The findings are valuable for possible rescue of the investigated whale and for policy and management regarding conservation of this subspecies as well.