A bearded man wearing a blue shirt and white t-shirt is working on a fishing net.
Someone is preparing to catch fish.
Someone means a person and a man is a person; the purpose of a fishing net is to catch fish; working on a fishing net indicates that something must be done to the fishing net BEFORE the fishing net can perform its intended function; if something is being done so that a function can be performed, then that something is a preparation for a resulting occurrence; therefore, someone working on a fishing net is rephrased by someone is preparing to catch fish.
The bearded man is someone preparing to catch fish with a fishing net.
The man working on the fishing net is preparing to catch fish.