D ( M ) in mens shoes means it's a medium width. Medium is the standard width for most shoes/boots. If you have any other questions you can always call Orthoticshop. We are open Mon-Fri 9-5pm Est. 800-309-0412. :)

C/D would mean a WOMAN's WIDE shoe. This would be narrow for a men's shoe. Men's standard width is D Measured width as a letter (or combination of letters), which is taken from a table (indexed to length and width) or just assigned on an ad-hoc basis: Examples are (each starting with the narrowest width): A, B, C, D, E, EE, EEE, EEEE, F, G (typical North American system, with the unlettered norm being D for men and B for women) 4A, 3A, 2A, A, B, C, D, E, 2E, 3E, 4E, 5E, 6E (variant North American)

Are these boots waterproof, Electric Hazard rated and Puncture resistant?

They sure are water proof no doubt about that  as for puncture resistant they can hold there own as well I've stepped on nails glass and a couple of broken pipes and I've yet to feel anything...one of my Co-Workers even dropped a 25Ib. block of cement and my foot survived without a scratch.