What do dolphins have to do with toroidal vortices?

Toroidal vortices are also known as bubble rings.  Watch the following videos and follow the links to find out how they are made and what they have to do with dolphins. There will be some questions to answer at the end.

Questions

1. What are four different examples of where toroidal vortexes can be found / made (either natural or man made)?
2. Which gender of dolphins seems to make more bubble rings?
3. How do dolphins make the bubble rings?
4. Describe an easy experiment where you can make a toroidal vortex.
5. What other interesting facts can you find about toroidal vortices?

Other resources to check out
Vortex Ring (Wikipedia)
Vortex Ring Experiments
Bubble Ring (Wikipedia)