You are not allowed to urinate until the injection is complete (though you can immediately after).

According to http://hypertextbook.com/facts/2001/DanielShaw.shtml 1 liter is at the very upper limit of the usual range of capacity for the human bladder, so most people aren't going to be able to hold that much and will risk rupture. Could be quite serious, and wouldn't be surprised if it'd lead to kidney damage and infection.

I feel like both ways you're screwed, but the seawater thing I'm pretty sure you'd just die.