I have issues with heights, and it irritates the ---steaming pile of meadow muffin--- out of me! I've been working on dealing with it by forcing myself to climb ladders and do it naturally. I feel thoroughly uncomfortable working at the top of a 6' ladder.
With my job, I have had to climb some pretty interesting job site ladders too. The worst was at an apartment building that I was surveying. There were no stairs yet, so the only way to the third floor was via a single ladder roped to the building. It was about 10 degrees, and snow and ice was covering everything. I was contemplating my fate at the base of the ladder when some construction guy zipped past me and right up the ladder while hauling 2 8' 2x4's over one shoulder. Hell, if he can do that so effortlessly, then I should be able to handle it. Of course, I was in a big jacket, and had to carry my clipboard and survey tools. I made it to the top, only to find the landing covered in ice. I slowly and shakingly swung around the ladder and got my jacket caught. I freaked out for a second, but recovered and made it onto the landing.
Having said all of that, I never had a problem with high dives at the pool, or jumping off a rock at the lake.

I guess the comfort of knowing I could only land in water made it better.