and, I would add: If you paddle solo, you should have a solid enough roll to be able to confidently depend on it.
As someone who paddles on salt water and freshwater (whitewater rivers) alike, it boggles my mind that there is a wide swath of "sea kayakers" who don't have rolls, or refined rolls that they can count on. An eskimo roll is not very difficult to learn and can greatly expand your comfort zone to accomodate a wider range of conditions. Way more valuable IMO than a GPS, VHF, Flares,or any of that stuff, useful as they are.
Increasingly I end up padding solo. My whitewater paddling is 95% with other boaters, with a few solo whitewater trips here and there. Most of my salt water paddling however is solo: maybe 80%. have one good old friend who I would sea kayak with more but it hasn't worked out that way. I do my more serious multi day trips with him usually, with perhaps another companion.
I like the solitary aspects of sea kayaking that others mentioned: Being fully receptive to the world under, above and around one's boat. I find that to be with a few friends who are discussing some movie or another while we are out is distracting.
Yup. Judgement, judgement, and after you've applied it, more good judgement! then some experience and skills.
It's a trip to be making some sort of wide crossing alone and have The Fear creep in about this or that. But I'd rather let that fear run amuck and listen to it, allow it to influence my decisions as long as they are conservative ones that keep me safe...