My number one priority for new divers is to own a good, big Surface Marker Buoy (SMB), and know how to use it. Practice deploying on every dive so you are familiar and comfortable with using it. Buy one that is at least five-feet tall so you are visible to boaters. The biggest mistake people make with SMB’s is not keeping tension on the line. If there is not tension on the line the SMB will not stand up. It will just lie on the surface and cannot be seen.