The pope exchanged his Popemobile for the a Pope-mo-boat for his visit to Venice.
A boat has long been associated with the Catholic Church. Peter as Pope is the new Noah or captain of the ship, and the Church is the boat Ark of Noah in the flood of the world's sin. Those within this ship are saved from the storm of God's wrath. We enter this ship through the water flood of baptism - the New Testament sacrament of regeneration.
The image of the "safe boat of Peter" comes from the Gospel story in which Christ protects the boat of Peter in the stormy Sea of Galilee (see Mark 4:35-41). Our first Pope Saint Peter himself uses the the same imagery of Noah's Ark in 1 Peter 3:20-21:
"Which had been some time incredulous, when they waited for the patience of God in the days of Noe, when the ark was a building: wherein a few, that is, eight souls, were saved by water. Whereunto baptism, being of the like form, now saveth you also: not the putting away of the filth of the flesh, but, the examination of a good conscience towards God by the resurrection of Jesus Christ."So then, the Church on earth is the "barque" or boat captained by Saint Peter. Granted, Peter is not always the perfect captain of the ship (Peter denied three times), but he is still the divinely appointed captain. Even if we Catholics should be scandalized by any Pope in the history of the Church, we would be fools to jump overboard into the stormy seas of the world. Peter is the sign of unity for the Church: "You are Peter and on this Rock I will build by Church and the gates of Hell will not prevail against it."
ad Jesum per Mariam cum Petro,
PS: In Catholic churches, the portion of the building in which the laity sit during Holy Mass is called the "nave," which is related to word "navy." It symbolizes the "boat" of the Church in which we safely sit.