You generally do not need a swimsuit for Tokyo DisneySea, as it is a theme park and not a water park. While the "Sea" branding refers to its seven nautical-themed ports of call (like Mediterranean Harbor and Mermaid Lagoon), the attractions are standard rides. You might get slightly splashed on rides like Aquatopia or during the drop on Journey to the Center of the Earth, but normal street clothes are the standard attire. During the summer "Get Wet" seasonal events, some shows may spray mist or water on the audience, but even then, a poncho or a quick-drying outfit is usually sufficient. If you plan on getting very wet during a summer show, bringing a small towel or a change of socks is a common "pro-tip" used by local park-goers, but wearing a swimsuit around the park would be considered inappropriate.

To prevent motion sickness on roller coasters, focus on stabilizing your equilibrium. The most effective tip is to keep your eyes fixed on the track ahead or the horizon; closing your eyes often worsens the sensory conflict between your inner ear and your vision. Before riding, eat a light, non-greasy meal—an empty stomach is just as likely to cause nausea as a very full one. Ginger-based snacks or over-the-counter motion sickness medication (like Dramamine) taken 30–60 minutes before your first ride can provide a significant chemical buffer. During the ride, try to keep your head pressed firmly against the headrest to minimize the "buffeting" that can jostle your brain. Avoid riding back-to-back intense attractions; give your body at least 20 minutes of "ground time" between big coasters to allow your vestibular system to reset.