Which parameter of Level 2 SRAL product for inland water level?

Dear all,

I would like to ask for retrieving the inland water (lake/reservoir) surface water level, which parameter of level 2 SRAL Sentinel-3 product (S3A_SR_2_LAN) should I use? And can I use that parameter’s value directly or any math calculation with other parameters for calibration is needed as well?

Regards,
Allen