Guys,
If you want safe electric immersion heater have a look at this one, page 13-5 (4108B - Nickel Alloy elements) and page 13-6. Electric cord is above the water. It is safe and reliable.
http://www.grimwoodheating.com.au/r111www/...s/section13.pdf
I paid mine around $90 (two years ago)...