Water
Sam loved to swim, so he really enjoyed the fact that Diego Garcia was located on a tropical island with a really stellar beach.
The Autobots didn't understand his obsession with it at all, being a race that associated getting unnecessarily wet with rusting. They often worried that he would be pulled under the waves and drown or get eaten by a shark.
Sam was never going to forgive Simmons for making them watch 'Jaws', he could still remember their panic when he walked into the base mere moments after the movie ended, his hair still wet from the salty ocean water.
Bumblebee and Ratchet had both ordered him to stay out of the sea; Sam had diligently ignored them. That had been a really fun night on base.
Bee had attempted to yank him, and Mikeala as well, out of the moonlit waves. He'd been forced to stop when Keala rather bluntly told him, and all of the other watching soldiers and Autobots, that they weren't wearing bathing suits, or any type of clothing at all.
They hadn't been, but that had hardly been the issue. Sam refused to speak to his guardian for the rest of the night and had to endure whistles and cat-calls from Lennox and Epps for weeks afterwards.