@Yocencia0 This is a really good question! Hopefully the mods can get some clarifications from Airbnb.
If you're interested in what's covered by Airbnb's liability policy (Host Protection), see here: https://airbnb.app.box.com/v/hpi-program-summary
I notice that it says injuries connected with watercraft are excluded unless the watercraft is "under 26 feet in length." It doesn't specify whether the watercraft is still covered for personal injury when it's taken off the property. No mention of bikes.
As for damage or loss, the Host Guarantee lists vehicles and watercraft among the physical property that is not covered.
From all I see, it would not be advisable to supply bikes or kayaks to Airbnb guests unless you have your own liability and property insurance coverage that extends to them, and collect a deposit outside of the platform.
A final consideration: every amenity you check off on that list is part of your binding agreement with the guest, so you're technically in breach of contract if you don't provide that bike or kayak. And you'd probably want to keep the freedom to not lend someone equipment if you had doubts about their ability to use it safely.