The phrase “海内存知己，天涯若比邻” translates to English in several ways, capturing the essence of the original Chinese idiom. Here are three idiomatic translations:

1. “A friend in one’s heart is as close as a neighbor across the sea.”

2. “In the vast sea of the world, a true friend is as near as a neighbor.”

3. “Wherever you are, a bosom friend is as close as the neighbor next door.”

Each of these translations aims to convey the sentiment that true friendship transcends distance, making someone feel as close as a neighbor even when they are far away.