I would go to the Aquatic Exercise Association www.aeawave.com which is probably the most respected certification of the kind.
The only one thing I never liked about them is that they are not honoring other organization’s continued education automatically. They will do it but only for an additional fee and then only for 1.0 CeCs even if it is much more than that. That money grab always rubbed me the wrong way.
But they provide excellent instruction.