Altaïr looked one way and then the other, eyes slightly narrowing as he tried to judge such things as current, water speed, to see if it appeared to come in more quickly than it left - and he made a quick decision. "One upstream, one down. To go by these--" He lifted his left wrist in demonstration, indicating the device there. "--Fifteen minutes unless an absolute solution is found. Agreed?"

It seemed reasonable to him. A group the size of theirs couldn't traverse too far in half an hour. Not far enough that Altaïr wasn't confident that he could find them again. These people left a very noticeable trail.