If you are not going to marinade for long, why bother. One, because it doesn't take long. And two, because you can add loads of flavor to everything you marinade quickly and easily.
When it comes to fish, there are two types, firm and flaky. A firm fish (think big fish) can take a stronger marinade for longer. Examples of firm fish are Halibut, Tuna, Marlin, or Sturgeon. Flaky fish, you know, the kind that tries to fall apart on the grill, can't take a strong marinade and shouldn't be marinated for long. Examples of flaky fish (think small fish) are salmon, trout, and cod.
Fish and Seafood Marinating Times
|Firm Fish||Steaks)||1 to 2 hours|
|Firm Fish||Fillets||30 minutes to 1 hour|
|Flaky Fish||Fillets||30 minutes|
|Shrimp||Large (Prawns||30 minutes to 45 minutes|
|Shrimp||Small (but large enough to grill)||15 to 30 minutes|