Translation

The Japanese word for "Dolphin" is iruka イルカ.

Romaji i ru ka
Hiragana
Katakana
Kanji
Meaning Sea Pig
School Level 小2,

Loan-word

The word "Dolphin" katakanized would be dorufin ドルフィン.
Romaji do ru fi n
Katakanaフィ
Hiraganaふぃ

Further Reading

Wikipedia: Dolphin (海豚)