Part of the next clue is placed in a washing-up bowl, which is then placed under a running tap. A selected treasure hunter stands a set distance from the bowl (for example, 10 floor tiles away). As the bowl fills, the treasure hunters must answer questions. For each correct answer the selected hunter moves forwards one floor tile. For each wrong answer the hunter can move back a tile or an extra cup of water can be poured into the bowl.
When the selected hunter has moved the full 10 tiles and is next to the bowl they are permitted to retrieve the drowning clue with their teeth (bobbing apples style).
Obviously the clue that is in the bowl needs to be something that sinks, but preferably with a part that sticks up which the hunter can grab with their teeth. A good example could be a key that sinks, but have it attached to a key ring that sits up from the bowl's bottom.
There are three important parts in planning this clue. Firstly, make sure that you have enough questions, and that the hunters can answer them. Observation of items around the house are generally quite good, as everyone will have a chance to answer. Alternatively include multiple categories that cover each of the hunters' interests. The second piece of planning is to test-run the flow of water and question answering as best as you can to ensure that there is a good amount of water in the bowl when the hunter has to dunk their head. Finally, make sure you set up a few cups of water ready before the quiz to use as the incorrect answer penalties - the tap will be in use during the quiz so you can't fill them up as you go!