Make sure the website works all the time (I just tried to book, and it failed and I've no idea if I have a booking or not).
Work out a way to tell people when there's a problem - or just insist that they check your website before sailing - WHICH YOU MUST UPDATE IMMEDIATELY IF THERE'S A PROBLEM !!
If there is a problem on the day, offer a free ticket for another trip. It costs nothing, but will make a happy customer and they'll come back aboard and spend.
The Waverley's enthusiast supporters and fans will put up with anything, but you need to appeal to those who just want a wee day out.