Properly lying down is better than sitting if you risk fainting. On your side, if nausea is an issue.
[He speaks fairly gently, if directly. Anyway, that's not what he wanted to say.]
Perhaps I am mistaken [although he doubts it,] but I do not think it is the sun or lack of hydration that bothers you.
[He remembers Eliot reacting to just talking about working, earlier, after all. And while Sebastian is all in favour of exposure therapy and ridding yourself of your inconvenient, good-for-nothing emotional hangups, Eliot is welcome to do that on someone else's free time.]
There is animal care that too needs to be seen to, should that be preferable to you.