What amperage switch for battery box?

Hello All!

I want to put an on/off switch on my battery box.  The battery is 50ah.  The Newport Vessels Yak motor has a 30 amp breaker.

Do I need a switch with greater than 30amp rating?  Wouldn't the switch blow at the same time as the breaker? 

Separately, but kind of related...  If I simply have a plug in, w/out an on/off switch, will the battery drain, when the motor's not plugged in?

Am I thinking incorrectly 'bout the weakest link blowing first?

Thanks, All!

Size the wiring and switch for the largest total draw.

Size the fuse for the smallest size of wire or switch in the system.

You can always add another, smaller fuse, just on the path to individual devices that you want to blow before the device, should the device short out.

Thank you!!