The expression 'whatever floats your boat' means do what brings you joy.
It's your birthday. We can go to the theatre or have a meal in a posh restaurant. Whatever floats your boat.
Peter is a ladies' man but if you still want to go out with him, fine, whatever floats your boat!
Don't confuse it with
The expression 'to push the boat out' means to spend more money than someone is used to, especially when celebrating something.
We really pushed the boat out and held Mary's farewell party in one of the most expensive restaurants in town.
It took less than three hours for the Titanic to sink after it hit an iceberg in 1912. More than 1,500 people died in the accident. For many, this event marks the passing of the Edwardian era of opulence (the first decade of the 20th century).