It's a fine dream to have. It would cost in the millions to get started. Most salvage treasure hunters get financing from people that want to invest in the endeavor to get a share of the treasure, But to do so, you need to have at least some probability of success. To do that, you need to have a sunken ship located or think you have one located. And it will have to be one that shows it was carrying cargo such as gold, silver or platinum.
There was a treasure hunter in the news today, that found a sunken ship several years ago and has just now going to try to salvage it. The US says the ship contained 3 billion dollars worth of platinum on board....the bad thing is that it was a British ship, and sometimes they lay claim to the contents.It is not a case of finders keepers in most situations.