But couldn't find an open bar.

但却找不到还在营业的酒吧。

It's an open bar, not cash bar.

那存不存在开放式酒吧的说法呢？

There was an open bar.

船上有酒吧。

When it flowers on the open bar, enjoy it;

花开的时候就让它开吧，欣赏它；

Offer a signature cocktail instead of an open bar.

提供签名鸡尾酒会而非免费酒吧。