Walaikum salaam,
All sea food has been made lawful to eat. Note the word 'Bahr' denotes any large accumulation of water, whether derived from seas, rivers, lakes or ponds. The pronoun in 'ta'amuhu' (literally it's food) relates to the word Bahr and this indicates all manner of seafood.
005.096
"Lawful (Arabic: uhilla) to you is the pursuit of game (Arabic: saydu) of the sea (Arabic: bahri) and its use for food (Arabic: ta'amuhu), for the benefit of yourselves and those who travel; but forbidden is the pursuit of game of the land as long as you are in the sacred precincts or in pilgrim garb. And fear God, to Whom you shall be gathered back"
I think you refer to verse 2:168, 'O ye people! Eat of what is on earth, Lawful (halalan) and good (tayyiban)'
The word used is 'tayyiban' (good) but it also says 'halal' (lawful). The Quran states categorically in the Quran what is 'halal' and what isn't. The word is 'fil-ard' (in the earth) which is a general statement for the earth, sea and everything found within it. I don't think this verse can be extended to scampi's etc.
Prawns, scampi's etc are a catch of the sea, therefore they are halal to eat in my personal opinion based on the Quran.
I hope this helps,
Joseph.