1. The answer to the first question in which you are seeking is YES. Tremors really do exist in the desert. Now, this certainly depends on which desert in the world your referring to, at a specific time in the future you may be trekking. For example: you may be traversing the Mojave Desert or near and feel tremors at a time in which there is an Earthquake in Los Angeles being a magnitude of 7.0 or higher on the Richter scale. Farther out in the Painted Desert near Flagstaff, AZ the magnigute of the quake in LA would need to be greater than 8.0 to feel tremors in the Painted Desert. Dont worry tho, The chances of experiencing tremors resulting from a quake within 500 Miles of your location in the desert is about 1 in 3,562,500,000 (1: three billion five hundred sixty two million, five hundred thousand) if my math is right.
IF however, you are referring to the kinda giant creatures that starred in the movie then your chances of coming across one of them is infinite. In the infinite number of universes that may or may not exist, there are a series of events that can happen that will result in the wave function collapse bringing into manifestion to your universem, your being actually observing a GIANT wormlike creature in a desert here on earth or on a like planet, or your omni present cognition.
Heres something to think about. You R God.
2. I actually had to look up how fast the fastest humans can swim. This is a good question and a reasonable one to ask, for you are concerned about your saftey. This is something you should not worry about still. This icy lake you are referring to will not contain any Beluga Whales. But if you want the long answer, then here it is. The answer is assuming no fins on your feet or assisted devices. The practical answer is no, however if you train very hard and are able to swim even faster than the fastest human swimmer on earth and a that particular beluga is for some reason a freak of nature, then yes. However a normal beluga is going to swim about 3 times faster at top speed for longer than you can travel at your greatest possible top speed (about 5 MPH).
3. I would suggest using a Remington 700 XCR Bolt action .223 Cal bullet. Better range than a regular .22 rifle, & It will give you the best distance and not blow your game to smithereens like a .308
The Bible, Albert Einstein, Art Frasik, www.remington.com, wikipedia, college, ect