For the most part many marinas require a copy of your boats' documentation, registration and insurance along with their slip application. Every state has diffferent requirements regarding insurance coverage and identifying the marina as an interested party or otherwise. A photocopy of the original is all that is legally required and a black and white scan emailed is also legal. The use of titles identying boats varies as there are a number of state that are "non-title" requiring only registry of some type. Other states require registration even if the boat is documented. Either way providing legitimate marinas with this information protects both parties in the advent of problems.