I just did the manta night dives in March on the Kona Aggressor. Sadly the first time we went, there were no mantas at all. But the next day we went to do the manta night dive by the Sheraton and we saw around 3 mantas. My tips to you. use your brightest video light and point it upwards, since the mantas are filter feeders, your video lights will attract the plankton thus the mantas will swoop by you. Make sure to point the lights above your head as there are some cases where mantas smack the divers head because they hold the light too low down.