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While taking my turtles for a daily walk today, Lily plopped herself into some drain-cover thing that has two shallow holes, slightly bigger than a hatchling RES. When I lifted her up, she smelt of Baygon, a mosquito repellent spray.
I was nervous and brought Sunny and Lily in. I placed Lily in a container with water and saw some 'ripples', like how oil stays on the surface of the water, being 'emitted' by her.
I am frantic. She has not been displaying any signs of sickness, for I doubt she drank any of the water, but has been staying at the bottom of the tank, eyes closed, as if she were going to sleep. Her head has also 'shivered' as if she had a spasm. D:

Take her to a vet.

Why were you walking your turtles?

You might have to separate her until you get this sorted out.

She is in danger. She's been poisoned. Poison is absorbed through the skin too. Take her to a vet ASAP.

Did you just leave her in the container of water? If it's an oily substance like you said, it's not going to mix into water completely without agitation; you need to thoroughly rinse her off to start with or she can continue to absorb the chemicals through her skin.