During my miss-spent youth, I regularly holidayed in the Greek islands � many thousands still do. Back then (as is no doubt still the case) you just bought a return flight to Athens, got yourself to the port and caught a ferry to your chosen island.
Although I had holiday insurance for each trip, I realised that I was not covered should the ferry back to Athens not run for any reason. On more than one occasion it was a close run thing, but luckily I never missed my flight. I searched for an insurance company that would cover such an eventuality � but could not find one.
Your situation would appear to me to be completely different to that set out above, your travel delay was outside your control (importantly, it was part of your fixed itinerary, it�s not like you could have caught an earlier ferry) � and I would expect most (if not all) insurance policies to payout.
I would agree with tigwig that you are being fobbed off. Sadly this seems to be all too common with many types of insurance.
My advice would be to go through your insurance companies complaint procedure and then to the insurance ombudsman (you have nothing to loose � and possibly �1,500 to gain). I would also seek the advice of the Daily Telegraph�s travel agony aunt Gill Charlton � if she says that you have no claim, then you have no claim.