I'm a BSAC Sports Diver, also did the Navy Divers course, and have met a lot of people in a similar state of mind.
Are you comfortable snorkelling when on the surface?
Is it that you panic when you dive with a snorkel and the tube fills that causes panic?
Scuba diving's actually less likely to cause that nervous panic reaction as the DV is constantly making air available to you whereas the snorkel will fill up with water and need clearing before you can breathe again, and it's a technique that some cannot master (bit like me and riding fast)
Give it a go in a pool, and I promise you'll feel much more comfortable that with a snorkel and it's a fantastic feeling when your weightless in the water.