Depending upon where you live, if you can find good (hopefully excellent) quality flash frozen jumbo prawns, you may find that they are even fresher than so called 'fresh' jumbo prawns at your market which may or may not in fact have been previously frozen in any case!
A flash frozen jumbo prawn, frozen right where it was caught, never un-frozen, and quickly thawed by you just before you cook it will rival a market sold fresh prawn in quality and flavor. The reason is that unless you are fortunate enough to get truly fresh prawns directly after they are caught (or better yet - catch them yourself) most fresh prawns even if not previously frozen, thawed, and sold as 'fresh' are really more like 'non frozen prawns' rather than truly fresh prawns. They may have sat around for a long time before you get them, and you have to transport them and store them yourself until you are ready to eat them. All that adds up to time for them to begin to go off - an opportunity never offered to flash frozen prawns.
Flash Frozen Louisiana Jumbo Shrimp (jumbo prawns)