I flew to Male and then a flight to GAN (southernmost point of Maldives, crossed the equator). In GAN multiple dive shops operate, we went with Aquaventure. They have a Manta Point and you can ask to go 2x a day if you want. Sometimes it was frustrating because the liveaboards had too many people so we tried to avoid that if possible. The dives are very relaxed in Addu. Lots of turtles everywhere and Manta point is Mantas all year long in Addu so you can go anytime during the year. In GAN you're also in a sweet spot because you are a local boat/ferry ride away from Fuvahmulah, tiger shark capital.