oil
Oil and wood are two substances that will float on water due to their lower density compared to water.
It is waters greater density than air that allows some substances to float on water.
Yes, if it makes the water denser, the boat will float easier. For example, it is easier to float in salty water.
Wood and styrofoam, to name two.
Substances that float in water typically have a lower density than water. Some examples include wood, oil, plastic, and cork. These substances are able to displace enough water to generate an upward buoyant force that keeps them afloat.
I suspect that "flow" is meant to also be "float", but even with that substitution, it just changes the question from nonsensical to counterfactual.Most things that float in water do not float in air.
Any object with a density lower than 1 g/cm3.
A human finger would generally float in water due to its density being lower than that of water. However, factors like oil or other substances on the finger could affect this.
Alcohol is less dense than water, so it will float on top of water. However, if the alcohol is mixed with other substances that increase its density, it may sink.
Many combustible substances (substances that will burn) are lighter (less dense) than water and will float - paper, wood and gasoline are a few examples. When ignited (set on fire), these substances will continue to float, and so will the fire.
All materials with a density greater than the density of this oil.
The fats (i.e. cream) from the milk will dissolve in the gasoline and the the resulting gasoline/cream solution will float on the water from the milk.