Ima tell the most dangerous location I built a base in first..
On my freedom world, I built a base that starts in the grassy plateau, a area that is next to a creepvine forest and a safe shallows, but here is the catch: it literally goes into the dunes, it gets worse from here..
Not only is most of the base essentially in the dunes (luckily my moonpool isnt), but it is literally right above a REAPER LEVIATHAN. This puts me at risk of a reaper ambush whenever i exit the base, and I did actually get ambushed once, all while surfacing while collecting quartz near my base! Luckily, the reaper has since then returned to the dunes.
By the way, the base has a observatory so I can observe it in my base.