Two come to mind.
Being knocked off my feet by a full grown adult seal was rather scary. Happened in the Don estury whilst fishing for sea trout. Saw a huge bow wave heading up river towards me in the half light of an evening, it popped its head up not more than 3 feet from me, sort of barked/coughed, turned and shot off. The swirl it made pulled my feet from under me and I ended up bobbing down the river towards the sea.
Getting caught in a big storm on Loch Leven and having the engine swamped on the run for cover. Ended up without power, on my own, getting dashed against the rocks ot the North of the harbour. I ended up jumping out and sitting on the bank waiting for the wind to die down so I could be "rescued".