The base of the gondola was an auto mechanic's creeper. On top of the creeper was a canoe-like frame built from PVC pipe (rigid) and PVC irrigation hose (flexible). I wrapped the frame with black felt, and held it taught with a rivet eyes/string system (similar to how shoes are laced). The top is cardboard, covered with the same black felt. Other details were cut from chloroplast / plastic cardboard (old election signs). Finally, I added some soft red fabric and a cheap-o dollar store dress-up boa.
All told, I had probably $40ish in this costume, the creeper, felt, and PVC pieces being the most expensive. As with most of my costumes, I actually had many of these things laying around.
For the gondolier: got a cheap hat and striped shirt online, paired with black slacks and long strip of red fabric as a sash.
Step 1: Supplies
2 - 10' sections of 3/4 rigid PVC
4 - 45 degree electrical PVC conduit bends (they make a more gradual front/back)
10 - 3/4 "T" connectors for rigid PVC
5 - 45 degree 3/4 rigid PVC couplers
2 - 90 degree "T" connectors (3/4 rigid PVC) (for the bow/stern points)
4 - straight -> threaded 3/4 rigid PVC couplers (because the only 90 degree "T" connectors I could find had threads on the lower section)
1 - 16' of flexible 3/4 PVC irrigation tubing
1 - set of PVC primer / cement
1 - couple yards of wide black felt (not exactly sure how much I ended up using)
1 - small amount of red fabric to cover seats
3 - large sections of cardboard (one for seats, one for the top in the back, and one for the top in the front)
1 - old election sign (chloroplast / plastic cardboard) - for the front fin and side dragon/mermaid decorations
1 - Probably 10' of string/rope/twine to tie the "skin" of the gondola taught
1 - Riveting tool and eye rivets
3 - pieces of scrap wood for seat base
20? - zip ties. Really, they are the new duct tape. :)
1 - can silver spray paint
1 - bottle of school glue
1 - shaker of gold glitter
1 - hot melt glue gun / several sticks of glue