There must be something that does this with Pi?

I got tired of checking the pool temps this year, isnt there anything off the shelf, that will monitor the water temp and have some sort of a web page output?

Ive found tons of things that should work (Monnit.com, temper2 devices, avtech.com stuff, thorlabs.com)
Everything seems to be like $400 when done, coworker just built this cool flight nav unit using a prebuilt Pi, he just plugged it all together and it works.
I cant find anything temp sensor related, that I can understand how to setup.

My ideal setup would be to have a sensor lead in the pool, connected to a reporting device, be that a Pi ~50ft away (by extending the sensor, or extending power/lan to the pool area)

Anyone have any ideas?

An RPi, even a Zero, seems like overkill for this. I'd be looking at something simpler like an ESP8266/ESP32. This Adafruit Feather, with its built-in LiPo charging, might be a good choice. It should be simple enough to program with the Arduino IDE. Adafruit, Sparkfun, etc. have some kind of temperature probe that can be directly connected. Arduino even has a tutorial on how to use it.

use arduino mini (5V or 3.3V version) or Arduino NANO and use Wifi though I2C or SPI or even 802.11.15 (Zigbee) and all the sensor connect to it, as for power, just use solar panel with a cap

Update - Found a guy on another team at work, he had setup a few Pi at his house, one being a solar pool heater, Picked up some items he suggested from Adafruit and they already arrived, will try my hand at coding, but he would help me too if I need it

Well, siphoning the water above the cover reminded me I never had anything to monitor the temps.
So I started another search, was just about to go with the 350-400 setup (from iMonnit) but then I found the XW110P form Control By Web
https://www.controlbyweb.com/xw110/ ~ $150
it arrived yesterday, took me 10 minutes this AM to configure, its outside now sitting in a plastic bin (its raining) and the sensor is just on the block wall.
+ is that the sensors I bought to try make work on the Pi, seem to be the same as the one that came with this, so Ill be able to have 3 sensors (pool water, air, maybe the 3rd for someones brothers butt?) LOL

Hey man, been following this. I even was about to post, but you had just bought the Pi. One day we should have an indepth talk about what I do. LMK if you ever have a question or need help. Would love to see pics. Have you tried openHab for this project?

This sounds interesting you could use the third sensor for spa temp Arduino seems like it would be a minimal footprint solution

Yeh, right now I have 2 sensors plugged in, had a customers old APC that wasnt working..found there was one of two dead batteries, the good one I bought a buck converter to use the 12v battery with the 5v 'external' input of the xw110, works perfectly.
https://www.adafruit.com/product/1385

Both sensors work perfectly too, I have a humidity/temp combo sensor Im wondering if I can get working as the 3rd sensor.
I just have to put it all in a water proof box to hand under the stairs of the pool...no worries about heat or ventilation...everything is cool to the touch, Ill probably put a mesh screen vent on the top side corners just to be safe.