Using TDS and Turbidity sensor in ocean: question from novice

Hi, I'm curious to measure the total dissolved solid content in ocean water as I go down in depth. I'm curious what your thoughts are - this sensor is made for clean water and the graph only shows up to 500 ppm, whereas ocean water can go up to 30000 ppm (?). This seems too far out of range, and I don't want to damage the sensor by effectively shorting between the pins.

I plan on using the sensor with an arduino 4.0 in salt water from 0 - 3 meters, but this project is just out of curiosity. I also plan on using the Gravity: Analog Turbidity Sensor for Arduino for the same thing.

Any thoughts, immediate fears, words of advice? I'm an ameture but want to learn!

Thanks!