You would need to contact an organization that ‘certifies” instructors. There are several. I do teach aquatic fitness instructor courses, but they are for certified Personal Trainers and Group Fitness Instructors. These course are for continuing education and to provide instructors who are already certified with the knowledge, skills, and abilities to teach clients in an aquatic environment. I would suggest that on top of any certification, you have your aquatic instructors also obtain a lifeguard certification.
IDEA does not certify. They are a professional association. This site will give you information about a variety of organizations that certify in a variety of fitness fields. It looks from your question as though you have tagged FITOUR… I would suggest the best way to ask them about their water certifications is to go to their web site and look for a contact section.
If you want to see other groups that offer certifications this is a link to the IDEA tool that lets you compare various certifications. I marked it to the spot for Aqua certs.