Try a reach rescue first
Source, American Red Cross
A reach rescue is the one you should try first. The Red Cross Lesson 8 PDF walks through it in plain steps: call for help, stay dry, brace your legs or lie flat on the deck, then extend something the casualty can grab. A reaching pole, a shepherd's crook, an oar, a branch, a beach towel: any of these counts. Once they have hold, keep low and lean back. The bracing is so your weight is behind the pull, not over the water.
It applies when the casualty is conscious and within reach of an extended object. The document is explicit that entering the water is not the lay person's job. Read it as orientation, not training. See Get trained for hands-on practice under an assessor. Reading a lesson plan will not give you the feel of a panicked adult on the other end of a pole.