True... white jeans is okay on the beach with a loose shirt, half-unbuttoned.

This isn't too bad either, but never with a western-style shirt and belt.

PIC:
Jeans, $225, by Prada.
Not too skinny, not too full. Perfect to wear with a blazer.
Sport coat, $795, and sweater, $620, by Prada. Shoes, $365, by John Varvatos.