Translation

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

Romaji i ru ka
Hiraganaいるか
Katakanaイルカ
Kanji 海豚
Meaning Sea Pig
School Level 小2, 中

Loan-word

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

Further Reading

Wikipedia: Dolphin (海豚)