1.) Raise your garden level high enough so the water goes somewhere else. This can be done using landscaping timbers, railroad ties, decorative cement block,logs,etc

2.) dig a drainage ditch to a location that u want your water to go to. Place a plastic perforated pipe in the ditch. Stub the pipe out where u want your final destination to be. Fill the ditch in with washed gravel gravel. Cover the gravel with top soil or what ever substance u want your finish grade to be.

A sump pump will work, but must be wired up properly, protected with a ground fault circuit.I would dig a deep square hole (3'x3'x3' for eg.) filling it 2/3's of the way up with washed gravel or larger rocks. I would place the pump over the hole and have it adjusted so that the pump will cut off automatically when the water level is lowered to your choosing.