how to gently break rock?

[c_scherer123]

How does one "gently" break LR to extract a eunicid worm?
I don't want to use freshwater as there are some nice fanworms and good hitchhikers and this is the piece of rock I chose to diversify my tank (though I didn't realize it also had the eunicid worm). The rock in question is the size of my hand (5-6" long 4-5" wide, fairly dense).