Definitely layers.
Yes, a 3-in-1 works ok, but they can get bulky and the outer layer typically isn't very comfortable. For example, I have a North Face Triclimate 3-in-1. However, I'm in search of a "better" one because the exterior shell is too hard, crinkly, noisy, etc. My brother-in-law has what I consider to be the perfect light jacket (from North Face). It's not a 3-in-1 I think. It's slightly thicker than a rain shell, with mesh inside so it's more comfortable if you're just wearing a t-shirt, with an attached hood. That said, the North Face rain shells (or anything similar) are a good option for Alaska.
I typically pack sweatshirts/hoodies for warmth. Than something light and thin to go over it in case it rains. I don't like umbrellas. I usually check the weather before a cruise in that region. If it's good weather with little chance of heavy rains, I might just bring a soft shell jacket over a hoody and just bring a hat to deal with any light rain that surprises me. Otherwise, just a thin jacket with a hood more to protect against wind. There have been days where it goes from long pants and sweater/jackets to shorts weather in the same day. I had a Sitka day where it was pretty cool in the morning, but by around noon, everyone was in shorts and a t-shirt. So it's definitely all about layers. Plus, big puffy jackets are really hard to pack.