Starcraft,

Water current is more important than tide -- some place have lots of current during a tide run and some don't. You don't want heavy current, especially when it's rough water. The waves yank on the buoys and vibrate the pots and repell shrimp. But then sometimes the bite dies when the tide is completely slack - so I like some current.

Peri, all garbage cans I have seen have somewhat tapered sides (so the garbage falls out).