My cursor was glitching out, so naturally I thought it was my resource pack and went to switch it out.

The first picture is the world upon loading up the game in joining (the resource pack that the game defaulted to, the one I last used).

The second picture is the result of switching to the default resource pack. You guessed it, a sea of blue wool. It should be noted that this is in fact still water, you have the slightly-lower-than-other-blocks look on it and the only resource pack I had on at the time of taking the second screen shot was the default one.

The third picture is a higher res resource pack. I thought it was worth a try on a higher res to see if that did anything. I guess, in the end, I got a skewed charging bow texture for the sea.

From what I can tell, this usually happens upon changing resource packs in general. Different combinations sometimes yeild different results, but the key thing is that you must change the water texture (an entire resource pack should work in the situation this does not) out for a new one. Or more-so attempt to.

Note: Upon this change (back in the default pack) I noticed that an enderman was holding a grass block, except the grass block had the "missing texture" texture.