Slatterz writes "Scientists from Israel's Technion University have unveiled a tiny robot, made using Micro-Electro-Mechanical Systems (MEMS) technology, purportedly able to crawl through a person's veins in order to diagnose and potentially treat artery blockage and cancer. The little robot — with a diameter of just one millimeter — has neither engine nor onboard controls, instead being propelled forward by a magnetic field wielded on it from outside the patient's body."
I've never been canoeing before, but I imagine there must be just a few
simple heuristics you have to remember...
Yes, don't fall out, and don't hit rocks.