The short answer to this question is that electrical tape is not waterproof. Although it is stretchy and elastic, meaning that it can easily be wrapped tightly around equipment such as hoses, the tape itself is not waterproof.
Waterproof electrical tape is not possible or practical because the adhesive is likely to lose its properties when wet and the seal will be unable to hold its shape under pressure. Instead, most types of electrical tape have a certain level of weather and water-resistance. This ensures that the tape can work with small quantities of moisture, but unable to perform in situations where larger amounts of liquid are involved.
You should always remember the importance of keeping wiring and electrical devices away from water and liquids. Water acts as a conductor for electricity and can be incredibly dangerous. You must follow the appropriate safety guidance at all times.
If you are looking for waterproof tape to use in a non-electrical setting, we also stock a wide range of PTFE tapes. PTFE thread seal tape is water-repellent rather than waterproof, but it is a much more suitable alternative to electrical tape for applications involving plumbing and ductwork.
You can find out more in our comprehensive PTFE tapes guide.