Answer: In the sentence provided, the participle is "digging" and the word that it is modifying is "man".
Step-by-step explanation: A participle is a non-finite verb form. There are two types of participles: past participles and present participles. While past participles end in "-en", "-ed", "-t", "-d" or "-n", present participles end in "-ing". Moreover, present participles usually act as adjectives and modify nouns. In the sentence "The man digging in the quarry helped us find our baseball", "digging" is a present participle because, besides ending in "-ing", it is functioning as an adjective and it is modifying the noun that is immediately before it: "man".