There is a big difference between various kinds of operations. You have choices.
Do you want to invest a large amount in a public company that does big projects?
Do you want to invest in a company with one particular goal above all others. (Melfisher.com or call and talk to Pat Clyne. I think their fun tickets are about $100k)
How about a private company doing research and exploration in a foreign country? Several of those around planning expeditions as we speak.
Maybe a private company doing research and exploration in the US?
Or would you like you to invest a few thousand with one of the subcontractors working on the 1715 sites? (If this is the one, I know a guy or two that would love to talk to you...

)
There are many threads on this forum and the "other' one that talk about how different operations are conducted, right and/or wrong. My advice is to read, read, read as many as you can. Talk to people. Read more. Talk to more people.
There are many levels of participation in this business, from divers to archaeologists to boat owners to sponsors to patrons. Some folks end up as victims. Do not risk more than you can afford to lose. This is hard work with a small chance of making the huge returns we all hope for. Sort of like working for lottery tickets.
Get in. Have fun. Enjoy the ride. Find people that you like to be around. Don't count your chickens until they are in the pen with the gate locked.

Cheers!