I've tried to do it as simple as possible without using boosts,losing lives or upgrading the oxygen generator.

Through some screenshots I will try to show the progression of my build as best as I can.



I started by putting my hero at the start ofc, I first build the melee towers and then I just started building cannons everywhere. There's a very tricky wave with the super fast mobs that can get passed if you don't have enough defenses spread out. You will also want the artillery towers with the swamp upgrade at the start to trigger the invisibles that will be coming later.



For the bottom right melee tower I tried to get out the golem ASAP as they are just great units and it allows your hero to move around more.



Just upgrade towers as you see fit pretty much, watch for areas that need more attention.
As you can also see in this screenshot I've built up some tesla's in the top left because this is where the nicotines usually become visible again and later on this is also where you will probably end up killing the bosses.



This screenshot shows what my defense looks like just before the boss wave starts happening.



And the last and final screenshot to prove that I did finish the map, all in all it's a pretty easy map on EASY mode that is. I've yet to try medium and hard but I will get to that at a later date and see how this defense holds up. And I will post guides about those as well.