Hey Hooligangirl,
Luuk has given you the short version
Most beaches are open to detect. Some district municipalities have put bylaws in place which requires permits. The first permit I got from the City of Cape Town was issued in 1996. Has anyone ever asked to see a permit - nope.
I said most beaches, the SA legislative environment is not friendly toward metal detectors. Play around on SAHRA's web site and you will see that any registered or un-registered wreck site is protected. The SA definition of the site include the wash or spill areas. In Florida you can detect on the land side of the wreck and anything washed up is yours (give or take the size of the concession that the salvage company has). Here it is all protected. Even sadder, if you find a pre-decimal coin - it should actually be handed in - not sure were - but that is the view of the average archaeologist in SA and they put the laws together. Have I ever handed in a old coin - nope.
Big jewelry finds: I have been advised that when finding a valuable find, put an add in the paper. Not a picture, just an add stating that you found - say a ring in the general location. It works the same as a deceased estate, run the add of the deceased and if no one responds within the required time frame, they can not come claim moneys later. Do I do this on every item of jewelry I find - nope. Have I done it - yes.
When it comes to getting the best value for your find. It is simple - the scrap metal in a ring is not worth that much. I try and locate the owner. The scrap metal value may be R90 but the reward based on the sentimental value of the item is often R500 plus. That's your best money for gold and a smile is worth a million bucks - I have often turned down the reward. For the gold that is left, find a jeweler that can get to know you and who will buy your gold and pay you the value of the refined gold. It makes a big difference. Good stones are even harder to sell. I have found that working with a few jewelers who get to know you and trust that you find your finds and they are not stolen, let them know what stones you have for sale and when they have customers who need a stone sell it through them. The difference is getting R500 for a 50 pointer or getting R7000 for the same stone. PS get your stones certified, a EGL certificate is not expensive as it is calculated by the weight of the stone and that way you know the value of the stone.
Sinkers are a good way to make friends with the local fishermen, the value of the sinker is a lot less than the value of their memories. They are on the beach a lot, give them a few sinkers, use it as a point to start a conversation and ask them if they have ever seen or remember hearing of some valuable item lost on the beach. I got one of my best finds like this and it was worth a lot more than the sinkers.
I have attached an example of a EGL certificate.
Happy hunting,
Alan