Hi there sir82. Thanks for bring up the fact that Jehovah has a fondness for beetles. Creationists however do not claim that every single species that exists today was brought into the ark or that they even existed back then during the flood.
They claim that the Bible word for "kind" refers to a basic representative of the animal in question. Example: One dog kind that later, after it's released from the ark, becomes the a wide assortment of species such as wolves, coyotes etc. That's evolution in the real world but in the Creationist world it's just variety (otherwise how do they explain a thousand and one breeds of dogs) and they set arbitrary limits on that.
As far as the capacity of the ark don't, for the sake of argument, underestimate what it could hold. Nor underestimate human ingenuity as far as maintaining that zoo. I acknowlege it's absurd but Noah did have, if I recall correctly, 120 years to figure it out.
The really devastating counteraguments are with the time frame involved after the flood. These counterarguments unfortunately are wasted on most people because they don't have the intelligence to visualize a handful of animals reproducing and spreading throughout the earth in the time frame allowed.
As far as the fresh water/ salt water issue is concerned just fantasize that Jehovah made the water canopy out of salt water. Nevertheless, such a flood would destroy aquatic ecosystems, but most JWs can't visualize or understand that.
If you're going to argue with anyone over creationism/ID it's best to keep the arguments simple. Vestigial organs, like that whales hipbone or the horses extra toe, make for a good argument.