I just saw a post from a friend working as a Dive Master in Lembongan island, right in front of Bali, with a picture of a salt water crocodile they spotted yesterday resting on the reef at a depth of 27 meters.
I had no idea they could dive that deep and now I’m wondering how far down can they go (and still come up 
)?
I do not know. But whales can dive to depths of 10,000 feet, and I would think a properly equipped reptile could match that.
This article says they can stay submerged for up to an hour, and eat stones to weight themselves down.
http://www.omgfacts.com/lists/12004/Crocodiles-eat-stones-to-dive-deeper
Colbri lives in Central Amercan croc country and knows reptiles well. Should be along shortly.
Edit: there are some citations that says they do not withstand pressure well. But seems to be some debate. Might be 75 feet is about the max though.
Closely related questions… What is the deepest any reptile has been proven to go? How about amphibians? Why are there no salt water amphibians?
Why would they need stones to keep themselves submerged? If they can go underwater, why not just stay under? And if the stones are making them too heavy to come up, how do they get back above water in the end?
Most sources believe these “gastroliths” stomach stones are an aid to digestion by helping to grind food. As such they are relatively small. A quantity capable of sinking a croc would to my mind be counter-evolutionary.
That’s what I found from googling–stones helping with digestion. And yes, it makes a lot more sense.
This source says they are thought to inhale more deeply to compensate for the stones when they are in float mode. And the stones may also serve to make it easier for them to float flat (counterweight to a heavy head).
Equipped with scuba gear and trimix?
I’m skeptical that an animal with absolutely no reason to make super-deep dives would be capable of surviving one.
Well documented.
But, I was stupid to think it might be possible for reptiles to do the same. Did not think about temperature regulation.
Turtles? Crab eating frogs.
Turtles are reptiles. Crab-eating frogs can “tolerate marine environments (immersion in sea water for brief periods or brackish water for extended periods)” - I don’t think that qualifies it as a true salt-water amphibian.
It’s also apparently “the only known modern amphibian which can tolerate brief excursions into sea water”.
Both quotes from Wikipedia. I had no idea there was such a thing as a crab-eating frog, so ignorance fought on that count.
I’d think that farting would also be counterproductive. “Whoops… shouldn’t have had that last rock…” as they slowly sink to the bottom…
Aussie report on Crocodylus porosus, the Saltwater Crocodile. They attached data recorders to the backs of 14 different crocodiles, ended up recovering nine of them, and discovered among other things, that the crocs could dive as deep as 50 feet. The post mentions that there isn’t much if any data on the diving behavior for this animal.
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Related study on a smaller species of crocodile, C. johnstoni: Ecological and physiological determinants of dive duration in the freshwater crocodile, Functional Ecology 2010, 24, 103–111. I’m stunned that Wiley made the full text available for free, but there you are. Not as deep a diver—of course, that could just be due to the river being much shallower than the bay where the Saltie study was done. But very long duration for some of them: one was on the bottom for ~400 minutes.
As mentioned, they have been documented down to about 50-60 feet (15-20 meters). That they might occasionally go as deep as 90 feet is interesting, but it doesn’t seem very frequent.
The record holder is certainly the Leatherback Sea Turtle, which has been documented diving as deep as 1000 meters/3300 feet. It has special adaptations that allow it to go so deep. As mentioned, most reptiles will be limited in their diving by cold temperatures in deeper water.
Amphibians have highly permeable skin which doesn’t allow them to maintain their body fluids at an appropriate concentration in full salt water. Reptiles, birds, and mammals don’t have to worry about absorption of salt through the skin (although they may need to excrete excess salt that they get through food or drinking salt water).
Interesting. I guessed it had to do with osmotic reasons. But, if a snail could figure it out, why not a frog? But a snail cannot breathe through its skin…
I know not many crocodiles left in Panama, but any encounters?