Charlie,
Stocking foot waders are fine in rocky or gravel areas. In sand locales, its tough to keep the sand out of the boot. This makes walking uncomfortable, naturally.
Salt water will also rust the eyelets on your boot, so they will cut your shoelaces.
You can get a cheap pair of bootfoot waders at tackle shops like Red Top in Buzzards Bay for $50. They are tough and will last several years.
If you want neoprene, you'll probably be happier with the bootfoot models.
A wading belt is also a good investment.