Finished up the cave I was in previously, defeating some Breadbugs (which were quite bizarre), and gathering a load more treasure. I have 91% of the debt repaid now. Wandered round Perplexing Pool for a bit, getting more berries and worked my way to another cave, which was in the water.
Now, it says at the cave entrance, that I need some of each type of Pikmin, but that clearly isn’t possible as only Blues can get to the cave. Took along 80 Blues, and jumped in. Realised that Blues CAN destroy flame jets (if you time it right), and then a huge watery thing (that looks like Chaos from Sonic Adventure) appeared, on rollers, and promptly flattened all my Pikmin. Tch.