Help! Duckling keeps opening her mouth!

[Cocelean]

She has enough water to dunk her whole bill in and swims in the bath tub every day for an hour and a half with Lukewarm water - sometimes twice a day and she doesn’t have a heater anymore but the room is fairly warm. She opens her mouth and keeps it that way - it starts from a small gap to full in opening it

She’s about 6-7 weeks old now

 

[CoriM]

What type of duck is she? I'm not sure on why she's keeping her bill open. How long has she been doing that? I think an hour and a half is probably a lot to swim at that age, unless she's in a little pond that she can easily walk out of when she's tired.

 

[Cocelean]

What type of duck is she? I'm not sure on why she's keeping her bill open. How long has she been doing that? I think an hour and a half is probably a lot to swim at that age, unless she's in a little pond that she can easily walk out of when she's tired.

She’s an Indian runner duck - and I do take her out at 30 minute intervals on a towel on the side where she shakes off, and goes back in again so I assumed she wasn’t tired of swimming yet. She’s been doing that for a couple of days now - today’s the most shes opened it so far - I tried getting iced water and having her dunk her head in a couple of times thinking maybe she was feeling hot even though my room’s at like 25C so it should be just about comfortable rather than really hot but there hasn’t been much of a change - she’s not doing it constantly but really often

 

[Crazy Maizie]

I would stop the ice water. It can shock the body and she could have other issues.

What feed is she on? What's her set up like? It almost sounds like overheating and she's panting to cool down. The room temp would be hot for humans. I'd also suggest less time in the bath tub. She might not seem like shes over exerting herself, but ducks do silly things. Normally ducklings swim or splash a little and then run around to jump back into the water they aren't in constantly for extended periods. Is this your only duck?

 

[Miami Leghorn]

Looks like the early stages of Zombie duck.

Compare

 

[CoriM]

I also think she's probably too hot. Where do you live and what are your plans for transitioning her outside? How are other members of her flock doing?

 

[Duckiiess]

Duck bath water does not need to be warm. Room temp/ on the cool side is more than warm enough for them. My ducks swim in the melted ice water all the time. How many do you have? If she's the only one, well that's a jerk move on your part, not sorry.

 

[Crazy Maizie]

Duck bath water does not need to be warm. Room temp/ on the cool side is more than warm enough for them. My ducks swim in the melted ice water all the time. How many do you have? If she's the only one, well that's a jerk move on your part, not sorry.

Let's be kind and remember that there are multiple reasons why someone might have a lone duck. The OP hasn't verified that it's the only duck - it was a question.
Adult ducks can swim in colder water, but ducklings can have issues due to not being totally feathered and how their metabolism works. Plenty of threads where the only thing they did differently was to give them ice cold water and the ducklings seized and died.

 

[Duckiiess]

Many breeders will refuse to sell lone ducks for a reason. Also said IF above.
I'm not suggesting ice water for a duckling, but it certainly does not need to be warm. It's not a good idea to leave any ducklings unattended in any water.

 

[Quatie]

If duck is hot, it will stop panting after you put it in the water. If the water had no effect, it is less likely the duck is overheating.

Another possibility is that is have seen this with my drake before as his voice was changing. No sound came out. Just an open mouth screaming silently.

I have also had a few of my ducks so this when they were upset. I usually found it with some of my broody ducks, which yours is clearly too young for that; but others of mine have also done it when really upset.

If the duck hasn't been doing it for very long, it is also possible there is something stuck in it's throat. Usually they shake their head trying to dislodge it. So I think this possibility is less likely.