My ranger from my friend's long-running Dungeons and Dragons, Second Edition campaign in his own setting developed an irrational fear of boats early on in these adventures. Since that time, she hasn't had to get on another boat, which is fortunate since the only way she's likely to get on a boat again is to be carried aboard unconscious. Even sailing ships are not necessarily exempt, as she is not fooled; those are merely big boats. Yes, indeed, the idea of getting into a boat can make this otherwise calm, levelheaded character freeze up and start saying, "No boat," like a terrified child. This is the story of the two events which led to this.
In the first, our party, consisting of my ranger, a minotaur fighter/mage, a druid of a large furry humanoid race, and a NPC drow who was leaving her chaotic evil society, was in a pair of canoes heading out of an area where we'd been mistakenly blamed for the freeing of an imprisoned death knight. (It wasn't actually our fault. We did try to stop it.) We were heading down a river, making decent time until the river entered an unusual network of caves. This would turn out to be a brutal area filled with waterfalls, whirlpools, strong currents, and drow intent on killing us.
My ranger and the drow were in one boat, which by itself would turn out to be a mistake, as neither character had better than average physical strength. Thus, neither was able to avoid one of the whirlpools ahead while the two in the other canoe managed to do so. Fortunately, the trip through the whirlpool was not fatal, though certainly damaging and quite unpleasant. With our party now unintentionally split up, the two more powerful characters were not there to help us when we found a patch of land inhabited by a group of drow. A fight naturally ensued, and while my ranger and our drow friend were victorious, our health wasn't so good. Despite this, we had little choice but to go on since we didn't want to stay in these caves forever and we couldn't find any other way out. Back in the canoe, it wasn't long before we realized we were heading for some falls. Again, the ranger and the drow lacked the strength to prevent the inevitable, and thus they both fell into the water below, my ranger just barely surviving. Fortunately, the other two characters had emerged from the caves in better condition and helped us out of the water.
That experience alone might have been enough to induce an irrational fear of boats, but while it was the most dramatically bad episode in a boat, the second bad boating experience would come quickly. The party had recovered from the trip through the caves, and despite being reluctant, climbed into the canoes again and began rowing down the river during our next adventure. Eventually, the party was going past a castle; no one knew which kingdom the castle was part of. Thus, expecting to be ignored, the party continued on. Instead, we were forced to watch helplessly as a large rock, flung from a catapult, arced through the air toward our canoes. It plunged into the water close enough to fling us from our canoes and render everyone unconscious. They would then wake up in a cell minus their equipment and gold; they never did get the gold back.
Naturally, since she was nearly killed both times she was in a canoe, one might understand why she might be afraid of getting into a boat ever again. Only time will tell if she will get to avoid ever being in one again.