Yes the basic things you need are a camera body, long lens and a tripod. A nice extra to have is either a manual shutter release cable or a wireless shutter release to keep the vibration down from pushing the shutter release button on the camera body itself if you are shooting really long range.
You don't have to break the bank to enjoy yourself either. As an example let me toss a couple photos out here. All these were taken with an entry level 10.2 megapixel DSLR (if you have to know, it was a Sony a-200). The longer lens I was fooling around with was a slow(f8-f22), old (30+ years old), fully manual 500mm Rexatar telephoto. Mounted to the camera body using a $5 adapter I bought online. The other lens I was using is an older (25 year old) 70-210mm f4, Minolta Maxxum lens I bought new back in 1985. The whole set-up can be had right now for around $650 including the lenses and tripod. None of the photos are very good, but they are shot over water which can be a pain to expose correctly (which I didn't in most of them). This is bargain basement long range photography. To get clearer shots the price goes up accordingly.
First one is of a beach and lifeguard stand that was just over 4.75 miles from my location as the crow flies. Taken with the 500mm mounted on a tripod.
this is a 100% crop of the above image.
Next is a sailboat that was about 3/4 of a mile out. This was taken at 210mm, handheld.
Next is of a 1000 foot long ore boat on Lake Michigan. Taken with a few different lenses, in these you can really see the difference between a "regular" lens, the 210mm and the 500mm for how close you can get.
Kit lens that came with the camera (I marked where the boat is for those not used to spotting a boat out a little ways.) This one was out in one the shipping lane which is about 6-7 miles out at this location.
using the 210mm handheld
And the 500mm handheld.