Total Internal Reflection in an Aquarium? Snell's Law doesn't help

Hi Guys,
Been palying around with Snell's Law and the equation. When someone observes an aquarium, either side panel and the bottom panel appear as mirrors. I worked out the refraction angles going from air to water, water to glass, glass to air and none of them were larger than 90 degrees which is required for total intenal reflection. I am stuck and don't know why this phenomenon occurs.
Any takers? Can any bright spark help?
Chris

Total internal reflection occurs when the incident angle is greater than the critical angle. Not necessarily when it's greater than 90 degrees. Is this from an exam question?

Thank you. How does one calculate then the critical angle? According to Snell's equation you set the Sin theta 2 angle to 90 degrees and perform the calculation.

one can't in this instance because the refractive index of the second material must be less than the first medium. n1 = seawater = 1.34; n2 = glass = 1.53. You can't use Snell's equation in those circumstances. Yet this effect occurs. Total internal reflection on the bottom and side panels seems to be irrespective of what angle you view from. The back panel you can see straight through. Help cleaver people

Thanks

Chris

I think it probably appears like a mirror for other reasons, not because of total internal reflection. Assuming the back panel is the same material as the other panels, it makes sense that you see straight through, because you're right, there is no critical angle.