Swamps are not bad if you take it slow. Listen for the sound of draugr growls and the sound of buzzing flies. Draugr start to come after you slow, and then run when they get closer, so don't take them for granted. Pick them off with a bow while they're still in slow mode. Flies mean there's a spawner nearby. Those are usually either in small stone circles, or in stone ruins.

Skellies and blobs are vulnerable to blunt. Keep a shield on you for archers. Use the hoe, level ground, to create paths that are safe from leeches and provide a quick getaway.

Always, always, have poison resist on you and keep it up. Use it, as well as your rested buff, as timers to make sure you're out of there by nightfall, since it's not easy to tell the time of day in there. I almost never see wraiths because I don't wander around out there at night.

It's not hard to run away from abominations especially if you've been making paths. They seem to lose interest quickly. If you have a nearby crypt prepared with ladders, or if you have a high jump skill, get up there and they can't do anything to you.

Boats are just a bad idea. Try to find a swamp with a forest or meadows nearby so you can park in relative safety and walk in. Most of the swamp horror stories I've seen involve boats. If the swamp you're looking at is not ideal, keep looking. The world is big.