What do I have to bring at least?

Swimmin trunks, swimsuit, goggles if possible, wetsuit for swimming if necassary (max. 5 mm thickness). The wetsuit will be prohibited if the water termerature reaches 23°C or higher, because it is used primary as a functional protection against the cold water and not as a flotation device.

Bike of any kind, it only needs to be roadworthy (all screws tightened, set tax rate, tires and spokes tight, both brakes fully functioning, lighting installation is not required); the traffic safety will be checked by independent referees before the start. If the bike is unsafe, you can repair the defects at the mechanic booth. If a quick fix for whatever reason is not possible, you will be excluded from the race. Furthermore: appropriate footwear and clothing, suitable and approved helmet (no start without a helmet!), drink bottle filled with water or sports drink, sunglasses if necessary (useful for eye protection).

Appropriate footwear and clothing, head protection against solar radiation if necessary.

This and that:
For a quick change, a purchase of a number rubber band pays off. This way the number can quickly be moved from the back (for the cycling) to the front (for the running). Alternative, a normal rubber band will work as well.