If you ever wondered how canal water locks work, this model shows the basics of the lock's operation.
We included a simplified version of the benchy. You can use the original design, but it is top heavy and not suited for floating.
Small boats: if you want to fit 2 boats into the lock, print the boats at 70% scale, but boats printed at such scale can choke small children (as per "small toy choking hazard" rules), so keep them away from children under 3 yrs. old. Boats printed at 100% scale are large enough to be used around small children.
It's difficult to make a 3D print waterproof: a good place for this toy is a sink or a bathtub, or when used outside.
We printed at 0.2 layer, 12% fill