You need level 2 exploration, complete puzzle 1 at least one of the flowers mastered. Take an adult villager to the cauldron they'll say preparing a stew. Drop the villager by the cauldron again, Adding food to the stew, next Adding water. It will say 3 herbs needed. Add two orange flowers and one black one. tthe villager will eat the stew and say NO NEED TO BREATHE take the villager to the waterfall the villager will go under the water to get the gong piece.

ive finished it if you can make a stew you need 1 of the black flowers near the water fall and two orange red flower near the red flower by the mosaic (warning not the red flower though)

No levels of tech required. What you need is a stew made from the black flowers (northeast) and two from the orange flower (south and center). Then, after a villager eats it, place him in the pond. He/she will climb out and dive in from the platform to retrieve the gong piece. Be sure to let him climb out and dive though.

Actually, you need level 2 exploration to be able to find the cauldron.

Yes, I found out that anyone can dive and place the gong piece, not just a Master Builder.

Just exactly what does Level 3 Exploration give us? I could ring the gong without it.

Not much. The only extra is the ability to see collectibles in Map View. Since I hardly ever look at the map it's always the last (or last-but-one) tech I get. Level 3 Science is similarly of little use. By the time it is reached there's only the sewing hut to spend the extra tech points on.