A few weeks ago, my car started making rustling and creaking noises from the left side of the engine. Yesterday, the creaking got louder and became constant while driving. The temperature also started fluctuating up and down, and I noticed some kind of liquid underneath. I’ve attached a video. What could be the problem? Did the water pump fail, or is there something else? Thanks!
120k on engine

 

Welcome to CL.
Having said that and listened to your video, I suspect your water pump is failing and starting to leak and that is the sound of the bearings as the lubricant gets washed away due to internal seal failure.
ASAP before the engine overheats...
You need to have a well rated local independent shop check it out. Do not go to the dealer. Use Google and Yelp to locate such shops and get 2 opinions and quotes if a water pump is needed.
Do not tell them you were told it may be the water pump. Just tell them about the noise and the leak and let them figure it out without being predisposed to what I think.
This engine has been used in millions of Lexus and Toyota vehicles since 2009 and almost every shop has worked on this V6.