Waterproof silicone is an excellent sealant. If you're working on any projects where you have to cut into or drill into materials that hold water, or come into contact with water, this is the only sealant you need. You don't even need to bother looking for any other kind. Anyone who's uses it before can guarantee that water won't leak through.
I also use it for washing machine attachments to water lines. Especially if the attachments are old and have been used a lot, they start leaking water because it doesn't tighten enough. Instead of paying for new ones, you can just seal it with waterproof silicone.