I'd like to find the economical method to excavate the rock under sea condition. Due to the vibration restriction, explosives cannot be used. 1.0 kine is the criteria for the vibration.
There are many ways. How strong is the rock, and what depth of water? How much rock do you have to remove? Is the water calm, or rough and how far is a safe haven?
Can you use delays between blastholes to bring down the vibration?
Excavators on spudleg pontoons can dig some rock.
Cutter suction dredgers are expensive to mobilise, but can cut most rocks.