I wouldn't say that the Olympus bodies and lenses are fully dunkable in water. They can survive rain, although I'd use a good UV filter and dry the camera right away. I've read stories of Olympus reps pouring a jug of water over a E-M1 or similar, and many people swear by the weather resistance of Olympus m43 cameras. But common sense should still apply.
My m43 journey began with the E-M5 because I was shooting in the rain one day, and had to put my camera away. The E-M5 was recently released and there were really good reports of its weather resistance, so I bought one, along with the Panasonic 12-35mm f2.8, which is also purportedly weather resistant. I held it out a car window while driving down a mountain in the rain, and while the footage looked like carp, the camera worked perfectly fine after.
As for silicone skins, they aren't as popular as they used to be, mostly because compact cameras are far less common in 2023 compared with 2011 when the OP started this thread. I have a silicone skin for my Panasonic LX10, and while it greatly improves the camera's handling, I certainly wouldn't trust it to add any weather resistance to the camera.