Does dropping a rock or catching a fish affect water displacement in a pond?

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Dropping a rock from a boat into a pond decreases the water level because the rock displaces more water while in the boat than when it sinks. When the rock is in the boat, it displaces water equal to its weight, but when it sinks, it displaces only its volume, which is less. Catching a fish that has swallowed water will also decrease the water level, as the water inside the fish is removed from the pond. The overall changes in water level due to these actions are minimal. Therefore, both the argument about the rock and the fish result in a decrease in water level.
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My friend and I are arguing over this question. If you're in a boat on a pond and drop a large rock into the pond will the water level change? If so will it increase or decrease? What will happen if you catch a fish that has swallowed a lot of water? I said that the rock will increase the water level b/c it's like dropping pennies in a cup full of water, is displaces the same amount of water that's equal to the mass of the penny. In the case of the fish that water is taken out so the level decreases. The difference is very small though. My friend says that the water level will stay the same. Who's right?
 
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Neither of you.

When the rock is in the boat (which is floating), it displaces its weight in water.

When it is thrown in & sinks, it displaces its volume of water.

Since the rock weighs more than an equivalent volume of water, it is displacing more water when floating than when it is at the bottom of the lake. So when it is thrown in, the level of the lake falls.
 
What happens then when a fish is caught that has swallowed a lot of water?
 
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