I suspect you're confusing transit and evacuation suites.
Today's helicopter transit suites are fairly light 'dry suits', they have waterproof cuffs and neck seals with soft 'feet' which you wear normal footwear over the top of.
typically the kit looks like this
http://www.offshore-technology.com/c.../safety/shark/
Helicopter pilots wear a cosmetically altered version (looks a bit like a uniform and is dark blue!)
Evacuation suites have the thick heavy boots and are generally serious items to get on and off.