I just had the an experience that can only be described using one very specific image:
Let me set the scene. I've been searching tirelessly for IRON the last while but my random attempts to dig have yielded no results. Taking Winckle's advice on-board, I decided to set off on a grand adventure in search of a cave. With the lake frozen due to the snow, I decided to head across it to the forest I could see on the other side. I reached this forest only to see it wasn't really a forest, but a few trees surrounding ANOTHER lake, with the sea on the opposite side. However there was what looked to be the entrance to a cave right in the middle of the lake! It felt like something out of a Zelda game, but I quite happily headed off towards it anyway.
A few quick bashes at the stone with my axe and, sure enough, it revealed a lovely cavern area just ready for me to explore. Unfortunately my initial search of the area only revealed a few bits of coal, but I settled in to dig deeper regardless. I was barely a few swings into cleaning up the area and the roof caves in, and the entire place floods.
I decided to try and dig back into the cave from another area, so I went to a bit of dry land next to the cave entrance and started to dig down. And down. And down. And down. Eventually, after breaking one of my axes, I realised that the cavern I had found must have been pretty small as I couldn't find a way back into it. Foolishly, I had also dug straight down and basically prevented myself from escaping (I try to avoid the block-hopping method). So I started to climb back up, in a direction I'm not entirely sure of, and slowly but surely I made my way upwards. I was starting to fear at this stage that I was under the sea, and was simply going to break through into water and drown as my tiny one block escape route would flood instantly. After a few minutes of climbing back up, I suddenly burst into a massive underground cavern and literally right ahead of me is IRON DEPOSITS.
Things were finally turning in my favour, so I continued to explore the area and it just kept getting bigger. Areas to the left, to the right, and below were all stretching out before me. I could see various iron deposits and I let them lure me deeper and deeper into the cave. I came across a few enemies but was able to take them out with a sword no problem. Then I found an area with lavafall and right next to it was a waterfall. I thought the waterfall might be a way out so I headed towards it and tried to climb up, but I then saw one of those green hissing snake bomb things. I ran, knowing what they would do, and dived into the waterfall to escape. Sadly, it jumped down after me and exploded. All the items, everything, gone! And even worse, they were all being washed away into the dark abyss below by the water!