All those deathclaws lol. Not a single one managed to land a hit on me so far, luckily. I do not want to find myself without my power armor in such a place.
But the best thing about glowing sea, Fallout 4 finally became fun like Fallout 3 was for me. I got reminded of how exciting exploring the capitol in Fallout 3 because of the glowing sea.
That fun was missing from Fallout New Vegas and Most of what I have seen in Fallout 4 so far.