G'day Scotty,
I've never tried this with fish fillets but have with calarmari, chicken, beef etc and it works a treat.
Get two kiwi fruit, peel them and chop them up in bowl placing your meat in there as well. Fill it up with some water, enough that the meat is submerged in there. Leave it for at least half an hour or longer if desired and mate i'll tell ya once cooked the meat will melt in your mouth.
Cheers
Robert