I don't have a simple solution, action or pre-set. I divide and conquer in PS. Create a duplicate layer. Mask off the Manta. Copy that layer. Inverse the mask. Now you have two layers that can be adjusted, one for the manta and one for the blue water.
A shorter method is to create a saturation adjustment layer and create a mask for the manta. Pick the best white balance for the blue water. Desaturate the manta only to some degree.
I am highly ambivalent about Wakatobi. First, you will love the rooms and food. It doesn't get much better.
I've always considered it to be 4 star diving. I would place Komodo and Raja Ampat in the 5 star category. I don't know Sipadan, but all the other locations would be superior to Wakatobi for macro. So, yes, it is conducive to good photography, but they have rules (flashing cirtters and god forbid you pull out a tripod). But I'd rate other places higher.
Wakatobi has a lot of wall dives, but these would be your wide angle dives, not your macor dives. The best macro sets at Wakatobi are for the most part not wall dives. Currents are quite varied. It is no bigger issue at Wakatobi than other locations and probably less.
The marvelous house reef can be done as wide angle dive a long the wall or a macro dive on top.
I'm not a fan of Lorenz. All of the staff are gone since our last visit with the departure of Iman Baldwin. I've heard they have gotten a little strict on their diving.
Only rarely does someone say they had a bad trip to Wakatobi. They might have had a better one somewhere else, maybe for less money, too.