The best way is either by ferry between Seattle and Bremerton, or via the Victoria Clipper, between Seattle and Victoria.

You can rarely go wrong travelling anywhere within the sound by water—outside a really monochromatic grey rainy day with high swells perhaps.

Travelling north on the Sound near the Olympic Mtns. is the best. It’s not uncommon (though not common by any means) to encounter a pod of orcas along the way.