The recipe is simple: half lemon juice, half soy sauce.
No need to mix the marinade in a separate bowl; just pour the ingredients over the fish or meat.
I used swai, I bought some frozen on sale a few weeks ago. We cooked some once already and it was pretty fishy tasting. This batch smelled really fishy when it thawed, too, but the marinade removed the fishiness, thank goodness!
I gave it about half an hour and the fish wasn't fully "cooked" yet, so ended up throwing it in the oven at 350 for 20 minutes. Here it is on a bed of quinoa with some broccoli to keep it company. I cooked the broccoli with a little soy and lemon juice, also.
It was fabulous! I think next time I will use more lemon juice than soy sauce instead of the one-to-one ratio, just to see how it tastes. But this is great as-is. It's versatile; I've tried it on fish, vegetables and beef with good results and I think it would be good on chicken or pork, too. It would probably be good with the addition of cilantro or fresh ginger; I might try that next time. And I plan to use low-sodium soy sauce next time, too; that's alot of sodium. But the fish was perfect; the marinade decreased the cooking time, the soy flavor is not overwhelming, and it was a nice, summery dish for one of the first warm days of the year.