This is quite normal, I'm afraid, a few and I mean a few folk, have got old fishing boats, built houses on top of them and used them as floating houses, with dogs, kids and assorted rubbish on the pontoons, I guess this marina is just checking to see you are not that type of "fishing boat". Once they realise it's a proper job, they may well welcome you with open arms. I used to have a piccie of the boat, which Im used to send/show to folk when I was looking for moorings, as I liveaboard, they immediately think, "liveaboard" rubbish boat! I was not going to pout my boat in a mud berth, not this one anyway!