We are in whale season and while we love watching them from our canoes, please remember federal regulations prohibit approaching within 100 yards. Determining 100 yards at sea can be a challenge given there are usually no reference points to help gauge distance. One simple technique to determine the distance to an object is to hold your arm straight out with your thumb pointed up. Now close one eye and try to use your thumb to block your view of the object. At arms length, the average thumb will block an object from your view that is about 12' wide at 100 yards. An adult whale's tail width, length of pectoral fin, and 1/2 the distance from the dorsal fin to the nose are all about 12'. So wait until you can see at least 12' of the whale, then put out your thumb and see if you can block your view of the whale. If your thumb completely hides the whale, you are probably at least 100 yards away. Otherwise you may be too close. Note: if the whale is small or you can't see at least 12' of it, you'll be too close too.
Now that you have a simple guide to determine distance, there are some other things you should avoid.