Richard, Great yarn! Amphicars, they weren't, but they would float a bit for a while, especially if the door and other seals were in good condition. When you pulled your stunt, you must have been fairly lightly loaded (I meant car but guess that should apply to you as well) as otherwise the tires are submerged so far that they don't make much net propulsion, just churn the water and the greater depth, due to loading, makes the leaks worse which lowers the car which makes the leaks worse and so on until disaster.
My car is a 1961 with a slightly warmed over 1600. Pretty mild, single standard carb and just a bit too much compression to run without detonation on Mexican regular (and most of what is labeled as high octane down there). I have tuned headers A N D a good muffler (I hate loud and obnoxious). The muffler is easily replaced with a vertical stinger if you want noise, I don't do it. The original body is long gone and the floor pan/frame-chassis thingy is shortened by about 14 inches (short wheelbase gives handling characteristics of a go-cart). Remember the crowded back seat with little leg room for rear seat passengers? Well, that is where the 14 inches were removed. It has a fiberglass body with no doors or top. I will be getting a top designed and built (convertible cloth top) hopefully before it turns cold or too rainy. I have a hinged platform back there with storage below for tow strap, jack, cans of instant spare, tools, etc. and two seatbelts on top for little people (not leprechauns... I mean children and or small adults). There is a square bed frame type roll bar around the windshield and just behind the front seat connected by tubing which extends back around the engine for a full engine cage with skid pans below. In theory you could roll the bugy over, right it, and keep on. I haven't tested that theory yet. I too, catch a little air (go airborn) on occasion, sometimes on purpose other times as an unexpected adrenelin event. So far llittle damage and what there has been I could fix.
My tires in rear are about 18 inches wide. and in front much much smaller. CG is behind the pilot so don't need much tread width up front (considerably lighter that original bug configuration). This thing started life with a transparent gold metal flake gel coat but is painted forest green with some gloss black and some flat black accents(?). The speedo is fairly accurate and as you recall is driven by the left front wheel so the huge rear tires do not make for a speedo error. I have had it indicating a bit over 85 on the highway. Got it to about 65 or a bit over briefly on the beach in Baja. More typical speeds on the beach is 5-45 (not a lot of folks on the beach for miles and miles of nice sand in places in Baja). I wish I had lower gearing so I could carry a bit more RPM when going slow off road, picking my way across rough areas and the like. Big tires exacerbate the problem but little tires sink in the sand too much and stress the engine or bury up and strand you.
Getting this thing "street legal registry" in CA was an interesting experience that I won't go into unless there are requests. Tags expire the end of Sept so I will be putting OK plates on it (way cheaper). I'm hoping that it makes a good ranch scout car with its light loading on the tires. Hope it will tread lightly as I think it will. I will miss the A/C in our trucks but the sacrifice may be worth it. Soon I will be shopping for an "Easy Rider Rifle Rack" for it. Would like to have a Kubelwagen (Thing) but they are getting harder than Bugs to maintain due to parts availability so I am at least a decade late on that one.
Hope to have it back on the road later this week but only time will tell. If I remember, when I get it back I will post a picture of it before it secumbs to the planned camo paint job.
And... no, this one only looks like a bath tub but wouldn't float very long.
Patrick
