I've used this timer for years with no problems. It gets salt spray on it all the time.
http://www.canadiantire.ca/browse/pr...romSearch=true
I prefer electronic timers over mechanical any day. Electronic timers are more reliable and accurate, Mechanical timers can vary their on/off times by a few min. each time they switch. Electronic timers do not have to be reset after every power outage. That can be a big deal since I'm running 7 times between 2 tanks.