The pony - nicknamed 'Fat Boy' - escaped from his stable and broke into a back garden with another pony where they began munching on hundreds of fallen apples.
Because the fruit had started to rot and ferment, the greedy horses soon began to show the effects.
Tipsy Fat Boy stumbled across the garden, lost his footing and fell head first into an outdoor swimming pool.
Homeowner Sarah Penhaligon, 28, woke up after hearing a 'huge' splash and found the moorland pony in the shallow end.
But Sarah, of Newquay, Cornwall, was unaware the horse was inebriated and fed it MORE apples to keep it calm while fire crews were called.
She said: 'When I looked outside I saw this massive animal in the dark and I thought the Beast of Bodmin was in the pool.
'I was terrified, but when I took a closer look I realised it was a horse.
'I didn't have a clue what to do next - who do you call when there's a horse stuck in your swimming pool?
'I dialled 999 and they asked which service I wanted and I said I didn't know - I just had a horse in my pool and needed help.'
Police and fire crews raced to the scene at 3am on Tuesday and spent two hours building a set of hay steps in the pool to rescue Fat Boy.
They finally hoisted Fat Boy out of the water at 5am with the help of several harnesses.
Sarah said: 'He looked a bit panicked. He was trying to get out of the pool but couldn't manage it and was getting very tired.
'I decided to sit down next to him and calm him down, so I fed him some apples to keep him occupied.
'The other horse just kept munching away from the tree and didn't seem to care about what was going on at all.'
Fat Boy had escaped from the nearby Trenance Riding Stables.
A spokesperson said that Fat Boy, who is 11-hands, must have smelt the apples.
She added horses are known to get 'punch drunk' from eating too many apples which caused Fat Boy to become unsteady on his legs.
Stable staff only discovered that he had broken-out of his field when they were called by police. A spokesman said it was his 'portly figure' that kept him warm.
'It looks like he was scrounging for apples in the garden and fell in when he trod on the tarpaulin over the pool," he said.
'It's a good job he's got a lot of bulk, as it kept him warm while he was stuck in the water.
'After he got out he was taken back and checked over by a vet, but luckily he's fine.'
