Anyway you don't feel leeches coming off? That's surprising.
That's why it gets so much more dangerous if you're swimming. If a crocodile is above the water, then it can only see your head. And it's just the right size to be its prey.
And if the crocodile is underwater, then it may be even worse. Humans usually look clumsy when swimming, just like an animal in distress. In other words, an easy prey.
A funny story: a few years ago I went canoeing up a small river with my younger cousin. There's not a lot of current because the river is shallow and there are beaver dams around every corner. Most of the dams are unused and broken up, but the river's so shallow in the late summer that they block quite a bit of water anyway and necessitate portaging.
My cousin, being young, gets bored and stops padding, though he's still willing to help portage. We zig zag up the small river, crashing into either side every few paddlestrokes, because I hadn't realized that being the heavier one, I should be in the back of the canoe.
Eventually we get to a large felled tree blocking the river, and we attempt to portage around it, but the banks are quite steep and thick with brush, and I end up losing the canoe down the river. The current is slow, still, but the canoe is floating away, so I have to strip down and jump in after it. Unfortunately my feet touched the bottom and I was covered in bloodsuckers large and small, some of which hid themselves under my feet and between my toes for the rest of the excursion.
When I got back to the house, I lifted my leg, put my foot in the sink, and said "get the salt!"