Welcome to Duckdom!
There are so many good discussions about starting out, I found one I hope you will enjoy reading.
https://www.backyardchickens.com/t/622321/new-to-ducks-advice-3-day-babys
Storey's Guide to Raising Ducks and The Ultimate Pet Duck Guidebook are my favorite books for good advice on caring for ducklings.
They need to be able to wash their heads frequently to avoid eye, sinus and ear infections. But they need to be supervised when bathing/swimming. Swim water needs to be around 90F the first few weeks, and they need to dry off quickly, and avoid drafts.
Water management seems to trip most people up. Ducklings cannot help it, they splash. Setting up a nice watering station is not that hard, you need something to catch the splash and keep it mostly off their bedding.
Ducklings grow very rapidly! They need water with their food to prevent choking, they need three times the niacin that chicks do.
There's more, but I need to go work with my little flock now. Please try searching the forum archives.
Again, Welcome, please keep us updated, ask as many questions as you can think of, and upload photo's if you can!