I grilled fish last night but did I do it right?

I cooked mahi last night on my cast iron grill, I let it thaw in my fridge for 24hrs from being frozen, I marinated it for an hour in a zip lock bag with zesty Italian dressing, then I put it on the grill (without tin foil). It was on for six and a half min on the first side and put it on for 6 on the other side. I could see that the insides were still pink so I flipped it and cooked it for an additional 5 minutes. The outside looked thoroughly cooked the inside was white. When I ate it the taste was pretty good. My freind told me if you do it right you should be able to cut it without it falling apart however I did not get that effect. I would appreciate any opinions or advice