Try the Commands Troubleshooting and Help page if you get stuff with server errors.
Minecraft Drowned NBT Data Tags
A few tags for Drowned Zombies. The CanBreakDoors:1 doors is useful for map makers.
Summon a baby drowned
Are they cute or a little tragic? There's a special tag for a baby drowned, unlike passive mobs they never grow up.
/summon minecraft:drowned ~ ~ ~ {IsBaby:1}Summon a baby drowned riding a chicken
Baby zombies have an additional 5% chance of spawning as a chicken jockey in Java. But here is the summon chicken jocky command if you want to make it happen. Note that the chicken has the nbt tag IsChickenJockey which allows despawn as per usual hostile mobs.
/summon minecraft:chicken ~ ~ ~ {IsChickenJockey:1,Passengers:[{id:drowned,IsBaby:1}]}DrownedConversionTime and InWaterTime NBT Data
If a zombie is in water for 30 seconds (600 ticks) it begins converting into a drowned. After 15 seconds (300 ticks) the zombie becomes a drowned. Both values have a default of -1, which means no conversion is happening.
What about Husks, and Zombies
Husks use a different id "husk", click here for husks
/summon minecraft:husk ~ ~ ~
Zombies use a different id "zombie", click here for zombies
/summon minecraft:zombie ~ ~ ~
Suggestions or found a bug
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If you're looking for a particular summon mob generator you can link to these specific versions of the command generator.