Luggage and bags:
Pack light.... Mostly shorts and light shirts....
For guys, a pair of dress slacks and a kinda formal shirt and shoes will get you into most places.
I went into Donatoni's at the Hilton in a pair of slacks, collared shirt and loafers....
For ladies,same as above but a semi-formal dress, etc.
Clothing/Shoes/Weather Gear: Bring water shoes!!!! Most of the beaches have lava rocks...Very sharp.
Toiletries and Medical Supplies: All this stuff can be found locally.... Not as expensive as everyone makes it out to be.
Photo Equipment: An underwater camera would be nice... failing that, there are some cases for your normal land camera....