Very little, if you accept the premise that the DM might say no. The port they might be in is very small, one boat a week. The last twenty ships that docked there might be nothing but lizard folk sailors peddling their swamp jewelry. That is what the others are saying. The world and the place the PCs are exploring might have other considerations only thought about by the DM. In your case, there can be many reasons the DM says no. Maybe the port has been blocked for a month due to political tension. Maybe the port had a natural catastrophe, so the sailors you often associate that make the long journey over here, have not come for years. because it wasn't profitable. Maybe in this port, the navy has considered your native port vessels as pirates. The list goes on and on. That is my point.
I am fine with the DM saying sure, we can make room for your background feature. But it is a two-way street, the player needs to make room for the DM's knowledge, which they might not be privy to.