Personally, since I like using the Cyclops a lot, I use the Mountains/Bulb Zone entrance because it's very open and easy to navigate through, and it doesn't have hardly any hostile creatures that pose a threat to the Cyclops nearby.

I use the blood kelp trench for nickel, blood kelp trench for crystalline sulfur, and the bulb one for lava zones

I use the trench because it’s the safest and fastest to the cove tree

Wow it appears it’s just me who uses the kelp zone

I use deep grand reef lol. It's really pretty and I like the crabsquids

Crabsquids are epic

Cyclops door. Also, it has an entrance to the lava zone. You just descend and go straight, and the lava castle is within view.

Exactly

I use the Northern Blood Kelp because it's easier to get my cyclops down there to release my prawn in a better location. I also memorized how to get there since a lifepod wreck is right next to the cave opening so I just kept going there. Mountains are pretty good to get to the important bits super fast though.