I've had some psychologically-triggered ones, too. My usual one when I'm really stressed out is that I'm being chased by either sharks or vampires. The shark ones involve skimming over/falling into water, whereas the vampire ones involve flying.
To see a shark in your dream, represents a person whom you see as greedy and unscrupulous. This person goes after what what he or she wants with no regards to the well-being and sensitivity of others. The shark may also be an aspect of your own personality which exhibit these qualities. Alternatively, you may be going through a difficult, painful, or unpleasant emotional period. The shark symbolizes feelings of anger, hostility, and fierceness. You may be an emotional threat to yourself or to others.
Just let us know when the shark dreams come around, OK? *smile*