The experience verified my long ago memory from Guaymas, Mexico. "Sweet" is the distinction between shrimp that have been boiled alive beyond those passing as "extremely fresh." The latter is a matter of freezing just-caught shrimp inside a block of ice.
Elusive for so many years, my source of live shrimp (for human consumption rather than bait), was Liang's Food on San Francisco's Stockton Street between Jackson and Pacific. When ordered, they're scooped from a clear lobster tank to a plastic bag and were being sold at $12.99 a pound. Despite a language barrier, the fishmonger effectively communicated that shrimp so packed without a source of air might not make it alive through my 30 minute bus trip back to Cow Hollow. To avoid such a problem, I went to a nearby Chinese housewares shop and purchased a cheap plastic pitcher with a top through which air could enter.
Awaiting my return to Cow Hollow, Angela already had a pot of hot water close to boiling. We added salt and then the shrimp, after straining away the water in the pitcher. After about a minute, we removed and once again strained the now-cooked shrimp. Another couple minutes to cool before pinching off the heads, separating from the shells, and YES!!!
Perhaps others are doing this here in San Francisco or wherever else, and it's been written about. If not, please credit Unique Culinary Adventures with breaking an exciting story .