Shipwreck is a Special Mission in Bloons Monkey City. In this mission, every tower except the Monkey Buccaneer costs double their original price. Players must defend against 22 rounds (24 rounds in Bloon Dunes) of stepped up Bloons.. There are four whirlpools located inside looped parts of the track. The whirlpools can pop all types of bloons with an activated ability but cannot affect MOABs Players earn $6000 and 500 XP upon completion, along with 50 (with an extra 25 if no lives are lost, 2 if no lives lost on mobile).
There is an error in the whirlpool, when selected in BMC Flash, it will read 'Whirpool' instead of 'Whirlpool'.
Interestingly, the Monkey Sub is also doubled in price. One logical way of explaining this is that boats such as those Buccaneers use are easier forms of travel to the shipwreck site than does non-boat forms of transport, including submarines.
The mission can be completed without using the whirlpool ability, but it is very difficult to achieve.