As long as you know the risks, know and follow the rules and have you gear serviced and/or replaced according to manufacturer/industry standards, I'd say the risk is fairly low. You have a much bigger chance of pegging as a result of gear failure and stupidity than of attacks from marine life IMO.
Here's an example: A while back, I went on a boat dive after not diving for a month or so as a result of flu. Seeing as the winter weather in Cape Town is beautiful during the week and monsoon over weekends (Murphy's Law), I was very eager to get a dive in even though my nose was still a bit stuffy. On top of that, it was a deep dive so I was psyched (IF you know your theory, you should be seeing red lights just about now)
Now, equalizing while descending is fairly easy as we can use our stomach muscles to put some pressure behind our lungs, but when going up, this is not the case... And there I was, stuck at 25m with a reverse block. It was the most helpless I've felt in a long time, running out of air and not being able to ascend without feeling like I'm about to pass out. Luckily, after going up slowly and then hovering with my inner ear pressurized, the pressure would eventually escape slowly though what sounded like a very small, bubbling passage.
And right then and there, I learned that there's no grey area when it comes to scuba rules. You either dive by them, or break them. They cannot be bent. And when you break even one seemingly silly rule, you're increasing your "micromorts" from under 10 to about 700,000,000