Hey detector choice is difficult, A serious gold machine and a serious beach machine are different it sounds like you may need 2 machines,
The sdc2300 would be a great choice for a gold machine and it can also be used for salt water but it is a PI machine which means you will be digging all targets, bottle caps, bobby pins and junk so if the beach you wish to do is full of junk you will get frustrated quickly, even if the beach looks clean it's not, hidden junk everywhere.
May be worth booking a detector course to learn more about the machines and how to use.
Best of luck with your decision