Diving48 is a fine-grained video dataset of competitive diving, consisting of ~18k trimmed video clips of 48 unambiguous dive sequences. This proves to be a challenging task for modern action recognition systems as dives may differ in three stages (takeoff, flight, entry) and thus require modeling of long-term temporal dynamics. Each of the 48 dive sequences are defined by a combination of takeoff (dive groups), movements in flight (somersaults and/or twists), and entry (dive positions). The prefix tree below summarizes all the dive classes present in the dataset.
The video clips of Diving48 are obtained by segmenting online videos of major diving competitions. The ground-truth labels are transcribed from the information board before the start of each dive. The dataset is partitioned randomly into a training set of ~16k videos and a test set of ~2k.

More details can be found here.