1/ Diving at Hearvy Bay QLD , looked up and saw something swimming straight at me. Thought "Funny, you don't normally see eels midwater, hang on, thats not an eel ....". The olive sea snake swam around me (at about 10 cm away), under my armpit, between my legs close to, well, you know where, a couple of more orbits then swam off. Actually I wasn't scared dispite it being my first sea snake as I knew that sea snakes are both curious and myopic and won't hurt you unless you hurt them.
However,
2/ Used to do some work for the guy who ran the Green Island Resort of Cairns. It was near sunset and I asked if I could have a look at "Oscar" and was told "OK, but stand back from the cage as he tends to go at people at this time". So I went and had a look at the cage. The cage is about 20 meters by 10, there is this massive corcodile in it, AND I COULDN'T SEE HIM. I was certain he could see me as I got this cold feeling down my back so I retreated.
But
3/ A few weeks later I was required to inspect the hull of a trawler moored in Cairns inlet. At the time there was a six meter croc living there. He used to follow the yacht tenders. Basically I got in the water quietly, did the inspection and got out. Same cold feeling.