Im thinking I might want to give scuba diving a crack. Do you have to be qualified or can you just dive with a tour company as a one off? Is it better to snorkel first or just jump right into scuba?

Its always been sort of a love/fear thing. I think it would be awesome to see everthing going on under the water but Im terrified of being left behind or freaking out about sharks lol

So anyone been on a scuba dive, or done the 4 day course? Any advice?