amphibians

No newts. I think the salt would irritate amphibians skin. In all my years of keeping them (frogs, newts & salamanders), all the Discovery Channel programs I've seen & years of scuba diving, I really can't think of any.

Agree with Pufferpunk. There are none that will survive Brackish. Salt will dry out their skin and they will die of dehydration. It would be cool unforunatly it doesn't work. Mudskippy's will get 6 inches max, so not too large. Also have you looked into Anablep Anablep (the 4-eyed fish). They will get a bit bigger than the skippies but are much cooler and don't need to come out of water yet are surface dwellers.

I hope this can help you out...

There is only a few that can survive.
One I know of is a Crab eating frog from Malaysia.
They live in the mangroves and eat the crabs that live there.
Do a search on mangrove wildlife.
http://www.ecologyasia.com/Vertebrates/crab-eating_frog.htm

http://www.nps.gov/ever/eco/herps.htm
Southern Leopard Frog (Rana utricularia)
Common in all freshwater habitats and in solution holes in hardwood hammocks. Also occurs in brackish water. Abundant, often seen at Shark Valley and Anhinga Trail.

http://blackwater.fws.gov/Reptilepg.html
Fowler's Toad
Bufo woodhousei fowleri
Abundant throughout the Refuge, in freshwater and brackish marsh areas, fields and woods. Feeds largely on insects. Primarily nocturnal.

Southern Leopard Frog
Rana utricularia
Common in shallow freshwater habitats. Also at edge of brackish marsh. Ventures well away from water in summer.

Pickerel Frog
Rana palustris
Common in freshwater and brackish marsh. Also found in fields and wood margins.

http://www.frommers.com/destinations/bermuda/0091030379.html
Amphibians--Because of the almost total lack of natural freshwater ponds and lakes, Bermuda's amphibians have adapted to seawater or slightly brackish water. Amphibians include the tree frog (Eleutherodactylus johnstonei and Eleutherodactylus gossei), whose nighttime chirping newcomers sometimes mistake for the song of birds. Small and camouflaged by the leafy matter of the forest floor, the tree frog appears between April and November.


http://museum.nhm.uga.edu/gawildlife/amphibians/caudata/sirenidae/slacertina.html
Greater Siren, Siren lacertina
"This is one of a few species of amphibians known to tolerate brackish water."

http://www.nafcon.dircon.co.uk/euro_urodela.html
Palmate Newt
W. Europe as far as Scotland and NW Iberia. 2½-4"?
See above for remarks on similarity to Montandon's Newt.
The main difference is the shorter tail filament (only up to 5mm) and webbed feet in the males. Females lack the tail filament and have a narrower caudal fin and smaller spots on the body. It is highly adaptable, living in ponds, marshes and brackish water in coastal areas but also occupying mountainous regions of up to 2,000 m. Life cycle and diet are the same as Montandon's.

http://www.environmentyukon.gov.yk.ca/fishwild/amphibians.shtml
Rough-skinned Newt (Taricha granulosa)
The Rough-skinned Newt has a rough, dark brown back, and a bright orange or yellow belly. It breeds in spring in shallow ponds, bogs and swamps. Rough-skinned Newts are found near permanent ponds, including brackish water, or in open mixed coastal forests with lots of leaf litter and deadfall. Adults may also live in water.

http://www.nafcon.dircon.co.uk/euro_anurans.html
Painted Frog
http://www.dropbears.com/brough/Canetoad.htm

Southern Leopard Frog would probably easist to come across

I've seen them all over GA and all up the coastline in canals of the east coast. I'd still recommend you acclimate them to brackish before tossing them in. Amphibians are super sensitve to water changes since they absorb mositure through their skin. I'm pretty sure bullfrogs can tolerate it as well.
Isn't the beginning of the amazon brackish? There has gotta be some amphibians living there.