@kablooey The biggest one that other policies would not cover is if there were a dive accident with another passenger that required the boat to turn around/change its plans. Most policies cover things that happen to just you or your travel companion/family. Mechanical issues whether that is engine/boat, air supply, etc. is also covered. A good op would at least pro-rate the trip based on what you were able to do but I have also read of some disasters happening on a boat where the op really ran and left people SOL. You also get coverage for lost diving days due to weather or if you are sick, but those also apply for their regular coverage under Dive Assure.
Most policies cover financial default and trip interruption and cancellation but the liveaboard rider also covers catch-up to the liveaboard. Some policies also include that, but not many or all, so double check.
Primary means they will pay out first, no questions asked, if you make a claim and can support it with the required documentation and information. Secondary means they will still pay, but they want you to claim with your health insurance or whatever options you have first then the remainder, they will pick up. I always buy secondary and have made a claim and it wasn't an issue. You just need to be up front with what you have and go through other avenues first and whatever they don't pick up, they will pick up for you. If you have no primary for that particular aspect of coverage, then they will pick it up.
