A very cool clip was recently uploaded to youtube from a kayak rentals business that demonstrates what happens when you approach killer whales in kayaks (yes, that's an Hobie i12 inflatable kayak). In short... much the same thing that often happens in dolphin encounters, which is to say they swim about, show off a little, check out the kayaks and move on. A far cry from what the namesake of the species implies, as well as the common misconceptions about killer whales and their temperament.
I can really identify with the guy shooting this clip (somewhere on the other side of the pacific ocean) because although I haven't been that close to killer whales, I have been that close to humpbacks and right southern whales - both of which are much bigger than orcas. I know exactly what it is like to get that close to such a magnificent creature and the way it made me feel. Like this guy, I get giddy with excitement and even though I'm always aware that whales and dolphins are not aggressive, their sheer size is intimidating and yes, I start shaking to. It takes cahones to let them get close, trust me. But when it happens there is nothing you can do but sit back and enjoy it - the experience is always worth it.
It's little wonder killer whales have such a bad rap when you see yioutube clips like this. If you haven't seen it before, go forth and watch it for entertainment. Don't be alarmed though because it's all just SFX, fully explained here.