Some people would know better than others why slipways like this are called slipways. Even though the concrete surface is made with a corrugated finish, there's nothing quite as slippery as wet green moss.
Besides unfortunate people slipping, and landing on their bums, many a vehicle has seen its end by being dragged into the water, unable to gain enough traction to stop from slipping down the incline.
Unlike others, I'm always extremely over-careful when walking on this kind of surface. ;)