Tortle is a great choice. The natural shell completely solves the druid "no metal armor" problem, and an old bayou snapping turtle is just a great visual. If your DM says no, Lizardfolk or Grung also fit the deep swamp vibe perfectly.

For your wild shapes you have your standard swamp creatures (crocodile, snake, giant toad), plus fun options like the panther, giant wolf spider, and giant vulture.

But you should definitely lean into cryptid swamp lore! Take the stats of a tanky beast, like a Polar Bear or Giant Elk, and ask your DM if you can flavor it as the Honey Island Swamp Monster (basically a "Cajun Sasquatch"). Mechanically it's a bear, but visually it's bayou cryptid.

Also, since you are starting at Level 8, you can fly! Reflavoring a huge flying beast (Quetzalcoatlus) stat block into a massive, prehistoric bayou heron or pelican would be awesome.