Speed runners of Mario games know how to maximize their movement. They know when to jump, how fast they need to run, and the movements of the enemies on any level. What they also know is that the Piranha Plant doesn't have a hitbox. If you bump into any other type of enemy, then you will die in the game, but not the plants that emerge from the pipes. The developers made the model for the character larger than the hitbox (the part that you can interact with). These speed runners know this, and it can look like they are jumping through the enemy, and perhaps cheating. They are only using their knowledge of the game and its rules to their advantage, and ignore the seeming danger.
Nachshon also knew what was a real threat, and what was something he could ignore. Having just finished the 10th plague and leaving Egypt after 210 years, the Jewish people were stuck. They were "trapped", sandwiched between Pharaoh and his army, and the sea. The people were scared, and expressed their fear with complaints to Moshe. After asking for Hashem's guidance, Hashem tells Moshe "Why are you crying out to me? Tell the Israelites to go forward!"
Forward? Into the SEA?? Rashi explains that Hashem was telling Moshe, ignore the sea, as it won't stand in your way, because the merit of their ancestors and their own merit in following me will protect them. Nachshon hears this, and starts walking to the sea. The water reaches his ankles, and he continues. Knees. Doesn't stop. Hips. Keeps going. Chest. Plowing on. [surely by now he should have thought that maybe he misunderstood or something] Shoulders. He's an unstoppable force. Neck!
The sea splits.
For Nachshon, the sea was not an obstacle. It didn't even register as a threat or danger. He could walk through it will full confidence that no harm will come to him. It had no hitbox. He knew, that if Hashem promised protection, then he has nothing to worry about.
Our sages tell us that if we have proper faith and trust in Hashem, then we should fear no person or circumstance. As we approach the Holidays of Purim and Pesach, we should remember that while we need to make an effort to accomplish, our success or failure is guided by Hashem.