AEA is in my mind the “gold standard” if you can get to them. AFAA also has an aquatic program that is a good overview of the basics.
Some gyms have pre-designed programs you can use if you shadow or follow along with an instructor, or go through an in-house training.
If you know a gym you plan to work for, I’d recommend you ask them what they are looking for; an older group vs. an athletic group would also change where you’d want to start.
Best of luck!