I thought out a suggestion: two new biomes.
1.: Great river: this biome would be like the river biome but the river would be (min.)150 blocks wide and it would go into ravines, become waterfalls and have islands in it randomly.too. It could have it's own sound (it's waterfalls too). The chanche to catch a fish could be 10% more than in a normal river.
2.:Mountain river: This biome could only be in mountains. if it reaches out of the hill biome it could turn into a river biome. If you would step into the river then it would take you with it. You could only get out of it if you get to a curve, if you would go to the side from the beggining or if it would turn into a river. It could be very curvy. You would have 5% less chanche to catch a fish.
Sorry if my grammar isn't good I am not from England nor not from America so I don't know English very much.
If you think that this idea is not good then please say it I won't be angry.