Hi! This is a very good question! Three herbs (sweet, soapy and spicy) are available to be gathered on the island...
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they appear in the following locations - one is below the red earth, one is next to the hut to the right of the Kraken Statue and the last one is on the left side of the Kraken itself. Make sure you've sent children in search of the herbs - only they can collect them!


From there, you can fetch some water to prepare the soup!