The easier you can move around in the water , the better. So don’t bring strobes and lights with you. They are stopping you from moving fast to where the action is. Just natural light photography is the best  for this trip.
Bring some freediving fins. Once you jump in the water you will have to swim fast! Best to use some longer fins. And you’ll need a wetsuit. Most people wear a 5mm in Baja.
For on the boat a bini and a windbreaker, sunglasses and reef friendly sunscreen. And bring a refillable water bottle with you so we can reduce the plastic bottles.