The hydroshield is Not necessity obviously. The material of it is sorta like the material of a umbrella.. i think if you sprayed water on it, it would repel.. just like a umbrella does. But i suppose it acts as an extra level of protection..

But as most people say.. if you submerge the pod in enough water.. i doubt the hydroshield can do anything in that situation.. its there to repel the water i think.