explain this low country boil please.
It goes by many names, depending on what part of the country you are from.
Hell it even has more than one name in it's native home of SC.
In Charleston, SC area (the low country of SC) it is called a low country boil. A little further south (and I mean a little, like an hour and half) in Beaufort, Hilton head, SC area it is called Frogmore stew.
It is ridiculously simple, and outrageously good.
Take a large stock pot (hmm, wonder where you could get one of those??)
fill it a little less than half full with water - get a rapid boil going.
Add potatoes, a couple of whole onions cut in half, Old Bay seasoning (or similar, Zatarains , etc) some sliced link sausage ( I like to use kielbasa).
Simmer until potatoes are done, add shellfish of your choice - traditionally shrimp and oysters in SC, but I prefer shrimp, oysters & crab legs.
When shellfish are done - drain the water, and dump entire pot on a 8' table covered in newspaper - and eat until you are ready to explode.
Oh and it is required to drink copious amounts of beer during the cook and the following food orgy.
EDIT: After reading your post, it is probably not a whole lot different than a crab (or crawfish) boil