Underwater Pier
For people who would rather watch fish than catch fish.
This would be similar to the clear Plexiglass tubes some theme parks already have, only instead of creating an artificial environment around them they'd be built close to fishing piers that are already in existence. You'd just walk straight out for a hundred yards or so, going down a gentle slope. At the bottom there would be a viewing room so you could sit around and watch what swims by.