DD 4 and a half constantly repeating her desires on holiday

My similarly aged DD does this. I agree it's immensely annoying! I think they don't have much concept of time etc yet so it's all a bit "have thought, say thought". I've had some luck with explaining what we're going to do first, then getting her to tell me what I've just told her. Makes her activily think beyond the thought that's going round her head. Although, then it can be followed by "we're going to the pool after breakfast! Aren't we mummy! First breakfast, then the pool!" Over and over...

Do you have any paper? I'd draw a visual timetable - playing, breakfast, get dressed, pool etc and keep directing her to it. She can tick off each activity. I like the timer idea too.

Do as others have suggested above as a first port of call, particularly the alarm, but then if she continues let her know that every time she repeats herself that 5 minutes will be added to the timer.

That tends to be quite effective for mine.

It's normal. She's just excited.

She has other stuff she can do, toys, iPad, drawing stuff, TV.
I mean... come on! That's normal, boring, every day stuff she can do at home but a pool, when on holiday so in a new place that she can never come back to... absolutely no comparison. It's very worrying that you can't see the difference.

Get in that pool. Create good memories.

Set an alarm on your phone, show her and say when it goes off we’ll go to the pool. And then ignore every request and direct back to the alarm. She should hopefully settle down!

She’s out of routine and probably doesn’t have much concept of time.
My DS is like this and I understand how irritating it can be! We try to just repeat eg yes, at 10.00 (and showed clock when younger). You could draw quick pictures on a notepad - dressed, breakfast, drawing while we pack up, pool.
She might settle more after a day or two, although DS is 12 now and every holiday is the same (and weekend, come to think of it). Less ‘I want’ and more ‘are we..?’