Original sentence: There is likely to be a helicopter landing platform.Yachts above  are almost always built to individual specifications, cost tens of millions of dollars, and typically have four decks above the waterline and one or two below
Edited sentence: A yacht of this size usually has four decks above the waterline and one or two below.It is likely to have a helicopter landing platform.The number of very large yachts has increased rapidly since the 1990s, and increasingly only yachts above around  stand out among other luxury yachts.Yachts of this size are almost always built to individual commissions and cost tens of millions of dollars (most super-yachts cost far more than their owners' homes on land, even though those homes are likely to be among the largest and most opulent)