The paper considers the results of experimental studies of pebble transport along the beach and reveals the role played by a submarine canyon near Pitsunda in the process. The coarse beach debris capture by the canyon head has not been analysed till now at neither Soviet nor foreign literature. The authors used the technique of colour indicators which was proved to -be effective enough. Quantitative estimations has been got for the rate and direction of natural debris longshore transport as well as for debris loss through the canyon head which is less than 10 m deep and cut the zone of longshore debris flow. The obtained data contribute into knowledge of the Pitsunda Peninsula coast dynamics and can be applied to coast protection designs.