I've just completed a felt and fabric kelp forest installation at the Santa Barbara Maritime Museum and while I don't need to see or sew another fabric fish for a very long time, I am so pleased with the result!
I had the fish printed on fabric and then I sewed and stuffed them so that they are three-dimensional. They are "hiding" within the 7-foot tall felt kelp fronds that hang from the ceiling, attached with Velcro and are part of the 'catch & release fishing' interactive.
The fish took an incredibly long time to sew, much longer than I expected, but it was worth it. They look great! If you're lucky enough to be in Santa Barbara, go check it out. It's very peaceful standing in the middle of the felt kelp forest.