Ponds and ducks

We have 6 Pekin ducks.  We got them as ducklings and started them in a kiddie pool. Then the big day came, the became big boys and girls and found the pond. They loved swimming around and playing then they got spooked by something and came out with wings flapping, feathers flying and it sounded like I had 1,000 ducks quacking.  I went to the pond and, of course, I couldn't see anything.  
.
A few days later, I saw a turtle stick his head up. It is just a common KY turtle but the ducks won't listen to me.

They spend the day looking out at the pond but have only gone in 3 or 4 times this summer and always come out in a panic.

They have a landing so they can go in and get out easy. I have caught a turtle and moved it to another pond but it either found its way back or a new one showed up.

Any ideas on how to get the ducks back in the water or why they won't go in?

Remove the kiddie pool?

Ha I've never heard of such a thing. Fascinating!

I put the kiddie pool away once they discovered the pond. I feel terrible for them in the heat but I haven't got a clue what's wrong with them. They aren't too bright so you would think they would have forgotten about it if something scared them.

And here they are watching as we feed the fish. Before the big scare they would eat with the fish