Fun and educational worksheet featuring Disney's Ariel and King Triton, designed to help children practice spelling and reading skills.

Problem Breakdown and Solution

#### Part 1: Missing Letters
The task is to fill in the missing letters in each word using the letters provided in the box. Each letter can only be used once.

Letters in the box:
```
a o n i e h r n l o e h a i e n t e
```

Words to complete:
```
Ari__l si__g wil__ sw__m
wi__h fo__ kn__w l__ok
wa__t h__m h__lp u__der
th__m s__e __e d__wn
sa__d s__e h__d __nd
```

Step-by-Step Solution:

1. Ari__l: The missing letter is "e". So, it becomes "Ariel".
2. si__g: The missing letter is "n". So, it becomes "sing".
3. wil__: The missing letter is "d". So, it becomes "wild".
4. sw__m: The missing letter is "i". So, it becomes "swim".
5. wi__h: The missing letter is "s". So, it becomes "wish".
6. fo__: The missing letter is "r". So, it becomes "for".
7. kn__w: The missing letter is "o". So, it becomes "know".
8. l__ok: The missing letter is "o". So, it becomes "look".
9. wa__t: The missing letter is "t". So, it becomes "wait".
10. h__m: The missing letter is "o". So, it becomes "hom".
11. h__lp: The missing letter is "e". So, it becomes "help".
12. u__der: The missing letter is "n". So, it becomes "under".
13. th__m: The missing letter is "e". So, it becomes "them".
14. s__e: The missing letter is "a". So, it becomes "sea".
15. __e: The missing letter is "n". So, it becomes "ne".
16. d__wn: The missing letter is "o". So, it becomes "down".
17. sa__d: The missing letter is "d". So, it becomes "sad".
18. s__e: The missing letter is "a". So, it becomes "sea".
19. h__d: The missing letter is "a". So, it becomes "had".
20. __nd: The missing letter is "e". So, it becomes "end".

Final Filled Words:

```
Ariel sing wild swim
wish for know look
wait hom help under
them sea ne down
sad sea had end
```

---

#### Part 2: Correcting Spelling Errors
The task is to identify and mark the misspelled words in the given sentences.

Sentences:
```
Ariel was saife undder the sea, but shie was not happy.
She wanted to be together with Prince Eric. Her father,
King Triton, loved Ariel very much. He died note want her
to be said. He made Arriel human again.
```

Step-by-Step Solution:

1. "saife": Correct spelling is "safe".
2. "undder": Correct spelling is "under".
3. "shie": Correct spelling is "she".
4. "note": Correct spelling is "not".
5. "said": Correct spelling is "saved".
6. "Arriel": Correct spelling is "Ariel".

Marked Sentences:

```
Ariel was [X]saife[X] [X]undder[X] the sea, but [X]shie[X] was not happy.
She wanted to be together with Prince Eric. Her father,
King Triton, loved Ariel very much. He died [X]note[X] want her
to be [X]said[X]. He made [X]Arriel[X] human again.
```

---

Final Answer:

#### Part 1:
```
Ariel sing wild swim
wish for know look
wait hom help under
them sea ne down
sad sea had end
```

#### Part 2:
Mark the following words as incorrect:
- saife
- undder
- shie
- note
- said
- Arriel

\boxed{See above for detailed steps and final answers.}