Water inflow prevention device for aircraft working when landing in water, pressure adjusting valve, and aircraft

A water inflow prevention device comprising:

• a mesh part provided in a communication passage, wherein a fluid flowing through the communication passage passes through the mesh part;
• and
• a container that contains particles and that is opened when landing in water,
• wherein the container is mounted at a peripheral portion of the communication passage, wherein the particles are configured to prevent an inflow of water through the communication passage into an aircraft when the aircraft lands in water.