I think that's a pretty normal fear for all mothers. I know myself personally, I'm extremely paranoid about everything to do with the beach. I hate the thought of sharks, sting rays and jelly fish. I can't stand the waves and I freak out big time just standing on seaweed because I think the seaweed touching my leg is some fish.
As much pleasure as it would bring me to not let my children into the ocean, unfortunately that's just being completely unrealistic. Even though I fear the ocean and the safety of my children, I believe it's important for your kids to be exposed to the beach and all it's risks from an early age. Little Nippers is a fantastic program to enrol your kids into...
Our beaches are constantly being scouted for sharks and we can be rest assured that when our children swim between the flags or in this case participate in the Nippers program, they are in more than capable hands. We have people trained specifically to ensure the safety of our children and ourselves watching us at all times and we have to learn to trust their ability and realise we're not going to be mauled by a shark if we follow their rules.
As they grow older I'm sure us mothers will continue to worry, after all, that's what we do best! I know I'm going to turn grey very early if my kids turn out like their father. My DF loves the beach, when he was a young child he used to swim as far away from the other swimmers as he could so that no one would steal his waves. The life guards used to be onto him within 5 minutes of him getting into the water, telling him to swim back into shore and that he was too far out.
Lessons in survival and what to do when you find yourself caught in a rip etc while in the ocean are best taught by the professionals. Myself personally, I never go any deeper than my knee height. My DF has been caught in many rips during his life time, he's gone as far out to the point where he couldn't even see land more times than I care to admit. He went through the Nippers program as a child and he learned most of what he knows through either that or his Surf Lifesaving lessons.
I think you're definitely on the right track by sending your kids to these programs. You never know when they're going to need to know these techniques and there might come a day where it is a matter of life or death. I know if my DF hadn't participated in them he would no doubt be another life claimed by the ocean. I hope you go with your initial instinct to send them to Nippers, I know that I wouldn't hesitate in sending my children to Nippers.