Complex sentence: The location of the party is a big clue as to the form of the ceremony: when the party occurs in a dockside bar, the officer's friends are expected to (carefully) throw him or her into the sea.
Split into simpler sentences: The location of the party is a big clue as to the form of the ceremony. Normally when the party occurs in a dockside bar, the officer's friends are expected to (carefully) throw him or her into the sea.