Remote Temperature Sensors

I have one of those wireless thermometer / humidity / barometer things that
sits inside the house, with a wireless remote sensor that tells me the
outside conditions. It's made by a company called Oregon Scientific, and I
got it at Sams for something like $ 39.

I'm wondering if anyone knows of anything similar, except with a submersible
sensor. Would allow me to read my water temp from the Lazy-boy, set alarms,
etc.

I'm just starting out, so kind of want to know how the water temp fluctuates
with seasons, when to stop feeding, etc. I've emailed Oregon Scientific, but
if they don't carry it, they may or may not tell me someone who does.

Thanks