Naval transport unable to touch water?

So, every time I try to use a naval transport I can't use it.

This occurred in a 15,000 funds -extra cities Eurasia/Africa game. I was playing Vietnam and attempted to move a transport from Ho Chi Minh.
Specifically, I load all possible units at the time and move the transport. I can move the mouse over land (of course the trail/dashed line following is red, and I can't set it) BUT the transport will NOT go anywhere near water. My mouse stops when I try moving the transport over water beyond the city circle. It doesn't deselect or anything, it just refuses to be moved on water. Everything else is moving properly, it's just the transport.