Prodiver and B&B are first out of the ramp/harbor ~ 6am. If the second dive is the St. Anthony, after an 80ft Molokini dive, you will be back before 10. If the first dive is shallower/longer followed by Red Hill drift you will be back closer to 11, especially if there are whales during transit.
HeyJT, you didn't mention when you would be on Maui. If you are here during a busy period there are usually 2 and sometimes 3 trips per boat per day. I like to take pictures and the 2nd trips have much better light for ambient photography. The real reason for the early first trips is to mostly beat the trades on the second trip.
My most fantastic trips have predominantly been seconds and the few fantastic first trips had crappy photos. Sometimes the wind howls on the way back to the ramp but winter has much less wind than summer and my mom skied a lot of moguls the winter before my birth so our mildly rough tradewind seas are no problem for me.
To each his own.