Mahibur is lost in the forest and is feeling very thirsty. But he finally finds a lake. So he dips the empty bottle into the lake but he is dumb enough to forget to remove the bottle cap. As he is is pushing the bottle more into the lake, he has to apply
More force
As he is pushing the bottle more into the lake the amount of water displaced is increasing and upthrust is equal to the weight of the liquid displaced. Hence upthrust is increasing. So he has to apply more force.