Multibiome superflat "water world" preset (custom superflat)

Hey guys, I have been trying to make a datapack for water world (90 water, 5 gravel, 5 dirt, 5 stone, 64 deepslate, bedrock) because I enjoy it the most, but lack the other ocean biomes, structures etc. So what I have been trying is adding these biomes: 
Warm Ocean, Lukewarm Ocean, Ocean, Cold Ocean, Frozen Ocean, Deep Lukewarm Ocean, Deep Ocean, Deep Cold Ocean, and Deep Frozen Ocean, Ice Spikes, Swamp, River, Frozen River, Deep Dark
these features: 
sea grass, kelp, sea pickle (warm ocean), coral reefs (warm ocean), ice spikes, if possible ice in frozen biomes, and maybe the river clay, sand, dirt disks
these structures:
burried treasure, stronghold, ruined nether portal (underwater), trial chambers, warm ocean ruins, ancient city and maybe some mansions
I cant seem to make this datapack working, if someone would help me I would be very grateful, thanks.