Cuttlefish.
First off, camouflage. To be fair you mention that the function of your camouflage is unlike chameleon camouflage, which is static. What you’re asking for is active camouflage, which does exist - in cuttlefish and some octopuses.
Hunting.
A few of these characteristics are less important for believability I feel (especially the dewlap) but some of them are potentially detrimental to the camouflage of the creature:
- Size.
It is much easier to look like something if you are the same size or smaller. This is why most camouflaging animals are small. Chameleons can sometimes get large, but always able to be obscured by a clump of leaves. If your dragon is just smaller than a Komodo, it may find trouble breaking up its outline.
- Packs.
Pack hunters don’t hide very well. More hunters means more chances of being spotted - camouflaged hunting favours a solitary predator. This is reflected in big cats. Only one big cat is a social hunter, the lion, and they have one member of the pack deliberately be spotted and push prey into the hiding members to hunt. They would not get close enough otherwise.
Since it’s an ambush predator, they wouldn’t benefit from hunting in the same area, they’d have better chances waiting different locations so that potential prey don’t overlap. 9/10 hunts are failures, having all three-four dragons waiting in the same area means if no prey move through that area they all go hungry.
Evolution.
First off, the confusing one.
Why are they good swimmers? Is their environment plentiful in large bodies of water? Or do they serve a similar niche to leopards? I assume they don’t since they ‘mostly live on the ground’. Leopards can drop down on prey from trees into rivers, which is why they can swim well. I can’t think of a reason for swimming to be selected for in a non-arboreal or aquatic creature, so I’d need more info on its niche.
So the niche of this animal is unclear. A ground-based camouflaged predator with adaptions common in ambush predation is the gist of what I can gather. I’ll try and tackle the other characteristics individually.
Those chameleon eyes are for ambush hunting - great field of view so you don’t need to move your head, great depth perception for aiming your surprise attack. Mantis have similarly functional eyes. A stalking predator has forward facing eyes, so unlikely to have independent swivels. Since you clarified ambush, this is a trait shown to be selected for in chameleons, so it is believable here.
The dewlap is a heat regulating surface in iguanas and a communicating display in other lizards, heat regulating can be important in large creatures and communication is important in packs - completely believable.
Sharp claws are a reasonable adaption for a predator, especially since it doesn’t have the chameleon’s tongue.
Size is dependant on prey size and availability. I already mentioned the detriments of large size to an ambush predator, though then again the wobbegong exists so maybe it’s plausible.your dragon would only have to grow this large in order to overpower their prey.
Tail is no problem, ancestral trait - loss of arboreal lifestyle means regression of prehensile trait. The green iguana uses its swimming ability (powered by this tail) for escape from climbing predators and apparently for finding prey (I can’t find what exactly they eat from rivers). It’s hard to draw predator parallels since green or marine iguanas are both herbivores.
