The marina is most likely not liable. As a general matter, a landlord is not responsible for the criminal actions of third parties. While sometimes landlord negligence (unreasonable carelessness) in not providing adequate security will make the landlord liable, that generally takes a showing of all the following:1) The level of security is definitively less than other, similarly situated landlords provide;2) The landlord knew, or logically had to know, of the defect; and3) The theft only occured due to the defect--that is, the thieves would not have been able to gain entrance any way. Thus, in regards to this last point, you'd have to show that the fact that the fence was in need of repairs was why the theieves could get in--and not they would have been able to go under the fence if it had been maintained. You'd also have to show that the marina was aware of that vulnerability.