If all the problem is is dehydration, then yes, soaking him will help. If he's on the bottom of the cage though, it could be too late. If you've soaked him for a few hours in warm water, he will be getting some of his water back. I'm not a fan of the shower thing, but if you want, give it a try. Seems to me like they don't wanna be there and it makes a mess. I put a small plant in the lawn and turn on sprinklers or spray the plant lightly with a mist nozzle on a hose. But again, if he's on the bottom of the cage, you should probably get him to a vet. Too bad tomorrow's Sunday it might be hard to do. Are his eyes sunken in? If he's dehydrated, his eyes should have sunken in a while ago and his skin will have small wrinkles in the skin, like it's loose. Keep trying the warm water soaking thing and get him to a vet ASAP. That's my suggestions.
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Tyler Stewart
Las Vegas NV
1.2 Nosy Be Panthers
2.2 Sambava Panthers
1.0 Tamatave Panther
1.0 Nosy Be X Unknown Cross
1.1 Veiled Chameleons
0.0.2 CBB Desert Tortoises
0.0.1 Sulcatta Tortoise