I was recently troubleshooting a problem with the air button on my in ground spa. No fancy control panel on this one. Just an air button to control the blower (Len Gordon #10 powertouch). There is water in the tube connecting the air button to the relay box fifty feet away. Is this normal? I don't know how it would get there if it hadn't been put there on purpose.

It (the water) not suppose to be in the air line, if the line runs underground it developed due to condensation. You can try it blow or vacuum it out, or run a new air tubing line.