Probably against the law for foreigners to kill them.

 

One of my dogs caught a small monitor lizard, I took it out of the dogs mouth and let it go in the field. They are harmless to humans and run away.
They will eat smaller reptiles, rats and mice and more.

 

I agree with JP, or a monitor. My wife is terrified of them but thankfully the dogs protect us. We've had some bigggg ones trespass (5ft or more) and the dogs promptly chase them away.
Good dogs
If interested have a local boy make a trap for you. All you need is a piece of bamboo (or pvc for tube), a trigger (normally bamboo) and a sapling or 2nd peice if wood for a spring. We never caught a momma sized one but did get a smaller one. Celebrate with a bar-b-que. If you've ever had snake, its about the same taste and texture.

 

Possibly a water lizard.