Solo traveller, wanting to do the marine walk but its a minimum of two package :(
Contact the operators and tell them your predicament and give them the dates you want to do it. They may have an enquiry from another single who they can put you with.
AussieMelb, not wanting to put you off, but do check their safety standards very carefully. Two people died on 24 October in Bali while underwater on a Sea Walker. One was a customer, the other was the "instructor".