Looks like the age has a multi-player problem: the 2nd player joining crashes. This is probably the swim region bug: when a link-in point is below the surface of a swim region (vertically below, no matter how far apart they otherwise are in the age), or when the age coordinate origin (0,0,0) is below the surface of a swim region, then the game crashes once the second player joins.
Ahnonay used to have that problem and Dustin did a bunch of patching to make that age work anyway (he shifted up the link-in points and he moved the entire age up).