Approx 10 large vessels navigating near the Barrier Reef daily. Many/most will use ICCP for cathodic protection which is known to oxidize/corrode nearby structures. Calcium & magnesium (reef structure) will oxidize very easily)
Typical large vessel cathodic system designed for 600 amps pumped into the seawater. Military vessels put up to 1800 amps into the seawater
EPA calculations for chlorine generation from ICCP electrolysis of seawater.
Using EPA calculations. 10 large vessels navigating along the Great Barrier Reef each day have the design capacity to generate as much as 420 lbs of chlorine, which is a strong oxidizing & bleaching agent, in the seawater. Chlorine will last a day or more and attack all organic/biological species nearby.