Be certified as PADI Advanced Open Water Diver OR
Have a qualifying certification from another training organization. This is defined as proof of certification beyond entry level (at least two certifications total). These divers must also have proof of 20 or more logged dives documenting experience in deep diving and underwater navigation.
From Course Prerequisites, page 1-2, PADI Rescue Diver Instructor Manual.
Experienced Diver:
The purpose of the Experienced Diver program is to allow you to certify divers who are not certified, but who can provide proof of scuba experience, or to certify divers certified by training organizations other than PADI as PADI Open Water Divers.
Course Prerequisites
Any diver with a scuba certification from a training organization other than PADI may enroll for Experienced Diver certification. In most instances, a continuing education course may better meet the divers needs.
OR
Any diver who has been diving for a minimum of two years and has proof of 20 or more open water dives, and who has never taken a scuba course, may apply for an Experienced Diver certification.
You may accept properly logged dives or military qualification as proof of experience. Other acceptable proof of dive experience includes a statement witnessed by a certified diver.
Use this certification carefully and with discretion. As the certifying instructor, you are responsible for the divers qualification.
Procedures for the Experienced-Diver Certification
To earn the PADI Open Water Diver certification, the Experienced Diver must satisfactorily complete the PADI Scuba Review program, PADI Open Water Diver Course Final Exam, and Open Water Dives 1 through 4 as outlined. You may allow applicants to meet these requirements
by participating in the final phase of a regular Open Water Diver course.
From PADI OW Instructor Manual, Experienced Diver, p 1-9