What specs would I be looking for if I were to walk into a Lowe's or Home Depot?
Look for this sign at Home Depot or Lowe's...

In the photo below the one on the left was bought at a dive shop for $7 and had >300 saltwater dives on it over three years when this picture was taken.
The one on the right was labeled as "marine grade" from Lowe's for about $4, and had done <30 dives during a one-week live aboard trip before this picture was taken. Note the handy "locked open" functionality, as well as the two spots where rubbing on the D-ring actual wore away some of the steel.
