Legend has it that Poseidon keeps a Ledger of all boat names on his 'Ledger of the Deep', so changing the name of a boat and messing with Poseidons Ledger is sure to bring on some consequences.
Therefore, Boat Christenings have been an important tradition carried on for centuries to protect the boat and its crew from harm (sea monsters, pirates and the like).
An individual ceremony can be created to reflect on the history or the making of the boat, the future usage of the boat and the meaning of the name chosen for the boat. It's a wonderful chance to get together all of your friends and family to celebrate the 'new life' of a boat.
Being a sailor myself I feel it's important to pour a bit of champers in the ocean to appease both King Neptune and Poseidon so they keep you safe in those big swells they sometimes throw up to surprise you.