Water Bugs
Whirligig Beetle
Whirligig Beetles are typically found in groups making crazy circles at the surface, although they are also capable of diving and flying. These are 'true beetles', not bugs. They are harmless scavengers.
-- Wikipedia
Note:
The rest of these bugs have a painful bite, like a wasp sting.
Water Scorpion
Above is the aptly-named Water Scorpion. These are generally found underwater in plant growth, although they fly very well, as do all waterbugs. If you are launching the boat through weeds, watch out for them, although you'd have to go out of your way to actually get bit.
-- Wikipedia
Water Boatman
In my experience, Water Boatmen are the most common waterbugs - you can find them in almost any still waters. They swim right-side-up with enlarged back legs. Water Boatmen feed primarily on algea, and are unlikely to bite.
-- Wikipedia
Backswimmer
Backswimmers are similar to Water Boatmen, but swim upsidedown, as their name implies. They are predatory, and have a painful bite.
-- Wikipedia
Giant Water Bug
You are more likely to see a Giant Water Bug on your porch than out on the lake. This is because they are strong night fliers, and attracted to lights. Like all waterbugs, they can bite, and given the size of them - 'Giant' - I imagine they bite pretty good.
-- Wikipedia