Cool as a cucumber
lɛŋθɹiː dʒɪŋfɔː dɛfaɪv zaɪəŋfɔː hjuːɐŋtuː ɡwɑːwɒn jɪwɒn jaŋfɔː
In Chinese 冷静得像黄瓜一样
This is a direct translation and is understood.
Example
"尽管压力很大,他仍然冷静得像黄瓜一样。"
lɛŋθɹiː dʒɪŋfɔː dɛfaɪv zaɪəŋfɔː hjuːɐŋtuː ɡwɑːwɒn jɪwɒn jaŋfɔː
In Chinese 冷静得像黄瓜一样
This is a direct translation and is understood.
"尽管压力很大,他仍然冷静得像黄瓜一样。"