I do see them as important skills (swimming more so than riding a bike), but non-negotiable? This doesn't fit the unschooling philosophy, does it?
How would you deal if your child wasn't interested in either, or worse, was fearful?
DH and I both really wanted him to be safe near water, and we really wanted him to feel comfortable near the water, too. That's something you can't force, and we didn't want to go that route anyway. It took a couple of years of constant exposure to the water and a lot of creative approaches and patience. We tried a number of swimming lessons, which by and large didn't work for him. We would always back off when he expressed discomfort, wait a bit, then try again. For a kid with an inborn dislike of water, he's always like the bath, so we gave him lots and lots and lots of time in the tub. Then we picked up a couple "turtle" pools via freecycle and filled them with various things -- water, ooblek, oatmeal, sand, etc., and let him go to town. Then we tried a friend's backyard inflatable pool. So he went from the tub to a wading pool to pool that comes up to his chest. And so on. He's still not comfortable in water over his head where he can't see the bottom, but now he'll go in a clear pool that's over his head and he'll trust us to hold him in the river or at the lake as long as we can touch the bottom.
So he's not there yet, but he's light years from where he started, and he wouldn't be there at all if we had either backed off entirely and let him keep his fear or if we had forced the issue and traumatized him. I honestly feel that we did the right thing in pushing the issue, because his fear was limiting his ability to participate in something that he really does enjoy. But I'm very glad we took the slow route with him and have let him process the experience at his own speed.
We also invested in a VERY good life jacket.