The answers to the following clues will have something in common:

1. Place to take a plunge, once
2. Atlantic-Pacific connector
3. Catalina and others
4. Ghost town perils, often
5. Deep spot in the Pacific
6. Person or project with a never-ending need
7.  High school senior class-cutting tradition
8. Concentration on one goal - to the exclusion of everything else

Answers:

1. Swimming hole
2. Panamal Canal
3. Channel Islands
4. Mine shafts
5. Marianas Trench
6. Bottomless pit
7. Ditch Day
8. Tunnel vision