Better be careful of what you take and I hope you know the laws.
Hawai`i Department of Land and Natural Resources
"State law prohibits the breaking or damaging, with any implement, any stony coral from the waters of Hawaii, including any reef or mushroom coral. HAR 13-95-70
It is unlawful to take, break or damage, any implement, any rock or coral to which marine life of any type is visibly attached. HAR 13-95-71
The taking of sand, coral rubble or other marine deposits is permitted in certain circumstances. The material may not exceed one gallon per person per day, and may be taken only for personal, noncommercial purposes. HRS 171-58.5, HRS 205A-44"
I see coralline algae on all those rocks...and that is a visible marine life form.