The most effective way for a legion to cross deepwater locations is by using the water transport. This is constructed using the CONSTRUCT command - see HELP EQUIPMENT for full details, summary of transport included below. The transports are then taken along with the legion, used when necessary if movement approach is correct. See HELP MARCHING for detailed info on how this integrates with the rest of warfare construction, terrain and movement.
Syntax: ... CONSTRUCT TRANSPORT [<further specifications>]
It requires a great deal of wood, metal and rope.
The transport is a large item and rather costly in commodities. The end-product is a vehicle capable of transporting heavy weights (like a well-equipped modest sized legion) across small bodies of freshwater. It has been known to be used on the coastal seas but at great risk to the occupants. A legion must have at least fifty individuals to carry out a transport construction, and each transport is capable of carrying up to fifty over deepwater. The transports are held in the inventory of the legion whenever used and this is automatic.
Syntax: ... APPROACH TRANSPORTING
Utilising the 'rivermastery' specialist skill, this approach allows your legion to use the water transport to pass over deepwater locations with minimal delay. The transports allow the legion to move and act more quickly than the rearrangements required for swimming (even, indeed, a swim is even possible) and have no detrimental effect on legion conflict. NOTE: a legion navigating deepwater using transports engaging a legion swimming will have similar advantages to cavalry versus footsoldiers.

