Least cost path with multiple points

Question

I am trying to connect bivariate location points together to form a route. My points refer to fish locations, and so I need paths that only pass through water, and not the surro

Answer 1

You could use a minimum spanning tree, where the cost on each edge is a function of distance and other factors. In your case, set the weight to infinity if an edge crosses non-water, making sure it never gets used unless they are required at the end to connect the graph. If the graph is non-connected, you can run two or more minimum spanning trees on each disconnected group of points. See wikipedia for easily implemented algorithms, notably Prim's algorithm.