I got into spearfishing/freediving about couple of years ago. I did exactly what you've just done. Started on a relatively small Hawaiian sling (or pole spear) and nailed lots of generally crap fish, but enjoyed it so much I got balls-deep in it from then on. In two years, I went from being able to dive 3 metres…

I remember hearing the old adage while spearfishing, or, it could have come from Jacques "Fucking" Cousteau..."The quicker your speared fish are out of the water, the safer you'll be. Injured, bleeding fish are a target for predators and they can be heard or smelled for great distances underwater." ...from a show in…

RE: your second point, I'll mention another cool example. The Clipper flying boats (Boeing 314) had engines that could be serviced in flight via crawl-ways through the wings. And they needed the ability to do these repairs for long crossings over the Pacific with mediocre reliability.