Aquatic Mob Roe

Roe would be an item you could primarily get from breeding 2 fish or any other (non-dolphin) aquatic mob or from Wandering Traders. You could then place it in water like with frogspawn which will then hatch into a baby version of that mob. Players who play on Superflat Worlds as a challenge would now be able to get mobs that were previously unavailable to them due to spawning conditions.