Bill, if you've found that pesky Isis 'wreck', then you have licked the hardest part of the whole thing in my opinion! You would not believe how many people I have had to give the coordinates to over the last year or so for that one!
Once I'd gotten as far as the Bismarck, it took me a few goes to complete all the objectives too. All you can do is launch over and over again, and keep checking the cruise plan map of the ship to make sure you have gotten all the targets, and all the areas of the ship photographed. For a while I wondered just what I had to do to get it all done, I had found all the individual targets, found the stern section etc, but in the end I got it done.
Titanic is just as easy to find, and is an easier wreck to explore because there are less hazzards on it, and of course we all know it like the back of our hand! But the stern section is tricky to photograph, what a MESS!