a thermal viewer will. i've used it to instantly see into my 2500-gallon poly tanks and the city's steel water tower.

it showed the water level thru plastic and metal, so i suspect glass too. it sees the temperature difference between the air in the tank and the water.

it even works perfectly with a cheap chinese thermal, like the AGM ASP-MICRO TM160 (https://www.agmglobalvision.com/agm-asp-micro-tm160), that i picked up on amazon for under $300