In AquaDome you encounter yourself in the middle of the ocean, all you have is a small glass dome with a tree, some grass and a single see.
Your job is to survive no matter the cost, some pro tips are:
Eat Dried Kelp, you can find it everywhere and in big quantities, and all you have to do is cook them.
Doors are your friends, mining in the ocean is really slow, however, if you bring a door with you you can place it and mine from the place you placed the door as there will be no water in that 1 x 1 area, allowing you to mine at normal speed.
Remember to use your saplings wisely, apart from shipwrecks, saplings are your only source of wood, but the problem can be solved real fast by just making some land (out of dirt) and placing some saplings, after you have more than 4 trees, everything is just much more faster.
Explore and loot shipwrecks, they have loot and valuable resources that you wouldn't be able to get normally in the ocean, plus they are another source of wood, they are really important!
And that's it, you will have to use your brain and think of more ways of surviving in this big lonely mass of water.