Copied from a site about SSB:

"No Pain, No Gain. Think Metal Surface Area. The RF ground installation is different for every boat but the basics are the same. You want to attach all big metal items on the boat together with copper strap and end up with a minimum of 100 square feet of metal surface area. Starting with the Automatic Antenna Tuner, the tuner should be mounted close to the feed point for the antenna which means it is usually mounted aft. From the tuner, copper strap will run forward and attach to the engine, any (and hopefully all) metal tanks and a keel bolt (any one will do). Getting the copper to metal toerails and the stern pushpit along with the lifelines can be of tremendous benefit. When incorporating the pushpit and lifelines, extra care must be taken with the route of the antenna feed wire."

To put that in another context, the best ground is to have a steel boat. Next best is to run copper bow to stern along the bottom of every bilge attached to any metal along the way. Do that in both hulls of a cat and the signal is awesome.

Copper braid over the side won't work - it's all about surface area.