On Page 55 of Total Warfare, units moving under Wing-in-Ground Effect - to include Land-Air 'Mechs in AirMech mode, as per Interstellar Operations: Alternate Eras - are able to "float" in water. Thus, they can take off and land from water hexes, as well as fly across the surface of such terrain with no penalties imposed.
According to the WiGE rules on page 36 of the current (6th printing) PDF for Alpha Strike: Commander's Edition, WiGE units (again including AirMech LAMs, which are treated as "regular" WiGEs in this game system) are permitted to move across water terrain. However, they are only stated as being able to land on clear or paved terrain without crashing.
Further, while it's noted that WiGEs in AS count the same as hover units prior to takeoff, it's not quite clear whether or not hover units themselves can "float" (as in, can take off and/or land on water terrain) in this game system.
So, to clarify, can WiGE units - or, for that matter, hovering units - "float" on water in AS under the current edition of the rules? Or, if they cannot at present, is this something that might be errata-able in time for the next printing of the AS:CE rulebook?