I think the key is to have a properly designed system. I have two electric pumps in the bilge. One is a 500 GPH Automatic in the lowest part of the bilge, about a 6" x 6" area. I call this the maintenance pump. I typically DO NOT leave the switch in the ON position unless on board, underway, etc.
Mounted above that, I have a 3500 GPH with a float switch thats wired directly to the house battery bank, this is the "emergency pump" or back up. It is always dry except for the occasional test that all is working well. Both do not have check valve, the larger one has smooth bilge hose, the smaller has the cheap stuff.
I am in a fairly fresh water creek on the bay as well, and yes, the bilge will freeze when the temp drops below freezing (my experience is below 20-25 F) for extended days.
I add Anti Freeze (I use the purple stuff) to the bilge, mixed with whatever minimal amount of water may present, maybe 2 oz. at best. I keep the maintenance pump OFF so it does not pump out any of the anti freeze. I check the boat regularly (especially after a hard rain or the temp dips low) to see if there is any significant amount of water in the bilge. If so, I switch the pump on to empty the bilge, then refill with Anti Freeze and switch it off again. In years past, I maybe did this once or twice over the winter.
Hope that makes sense?
This link that should help with what I missed or miss worded Installing a Bilge Pump by Don Casey
NOTE: I am in a slip and leave the shore power plugged in, attached to a monitored inverter/charger. I am not naive enough to think that the 3500 is gonna save the boat, except maybe long enough for someone to notice theres a problem? ;(