Recently? In the past three months I've swum in the Ullapool River, Lochan Sgeireach and Loch Leathad a' Bhaile Fhoghair in Stoer, Sandwood Loch, Abhainn an t-Sràthain, Thurso River, Helmsdale River, Loch Lomond, Dumbrock Loch... there's probably more but I cannae mind - it's been a good summer for swimming. They were all considerably warmer than the sea.