As liquid water freezes, the molecules arrange themselves in a way that takes up more space than llquid water. What would most likely occur if the arrangement of frozen water molecules required less space than that of liquid water molecules?
The Titanic would still be sailing, possibly.
If ice were denser than liquid water, icebergs would likely sink (even given that sea water is denser than normal water). If this were the case then oceans would likely freeze over. (For example, ice laid down in the winter months would not completely thaw in the summer months, and the next winter cycle would result in a net increase of ice).