Lazarus Chowder allows you to stay underwater for approx 220 seconds. Having swamp fever allows you to stay underwater for 106 seconds. Combine them together and you can stay underwater for about 440 seconds or just over seven minutes, with no levels into oxygen stat.
I recommend making large crop plots, tame a dung beetle, and use a berry-gathering Dino. When you grow the vegetables, find a bee hive, let the bees kill you and loot your body (bees won’t agro if you grab honey from your body), and now you have a guide on how to make Lazarus chowder.