1) 3V button cell with battery holder
2) 1k resistor (to limit brightness so as to extend battery life, we are not using it as a torch, just bright enough to see it bobbing when rod moves!)
3) LED (5mm or 3mm is good, choice of colour up to you)
4) micro swtich
5) prototyping board
6) shapelock or polymorph plastic (to cover electronics and protect from seawater, can use plasticine if u want too)
**wire everything up in series.. there are lots of LED tutorials out there!
For more projects, visit http://retardokiddo.blogspot.sg/ !!!