Right now liability is not the issue, preserving the claim is. Copies of any releases as well as marketing materials, names of as many witnesses and contact information, medical reports, Dr.s names and contact information, pictures of injuries, certifying agency names, real names of the parties with the dive operator, and any other information that could be lost if not acted upon now.
It's too early to tell the extent of the damages, hopefully there will be a full recovery.
I see huge jurisdictional and venue issues, but those will be addressed when you meet with an attorney once she is state side. Depending on the waivers in fine print that are implicitly agreed to (but never read) when the cruise was booked, the waivers and country of residence or incorporation of the the dive shop, and possibly the liability laws of the ships home port and dive shop, there may, or may not be a claim. Even if there is a claim, is it worth pursuing? Collecting a judgment in a foreign country is another factor to discuss with your attorney.
I seem to remember a law firm in Florida that specialized in cruise ship negligence cases. Most firms that market themselves nationally will associate with local counsel for an initial consultation. You might do a search for cruise ship law firms or related searches and make contact. They will have the jurisdictional and venue issues already sorted out.
None of the above should be construed as legal advice. You should consult a local attorney for advice specific to your case.
Good luck,
Jay