How many keep a sponge in your canoe? Fancy brand with chamois cover (NRS/Skwoosh/Harmony etc) or just a plain old big sponge?
We own a chamois covered sponge but have found it not very useful for our purposes. When we go tracking up the river with a lot of in an out with wet footing boots on, there is so much bilge water that the sponge doesn't cut it anymore. We use a cut off vinegar jug as a bailer. We can scoop up most of the sand and mud along with the water.
To tie the sponge to the bailer, or the bailer to the canoe? That may be a ground cloth innie vs outie debate. I’m in the tie neither camp.
Our canoe club in Vancouver was focussed almost primarily on weekly runs on whitewater. New club members would sometimes show up with bailers tied to a thwart. I would tell them that the club demanded that nothing could hang below the gunwales when the canoe was upside down, as this would interfere with canoe-over-canoe rescues. They sometimes protested. "But what if I lose my bailer?"
I generally replied, without any sarcasm at all, that "What you're saying is that you value your 50-cent bailer more than your $1,500 canoe."
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For a bailer gimme a big liquid laundry detergent jug. Thick durable plastic that holds its shape, big comfy handle and unlike a circular bleach bottle the detergent jug rectangle provides both flat sides and corner edges; the latter is helpful scooping out the last bit of water and debris way up in the sharp confines of a stem.
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I carry a pump instead of a bailer mostly because I'm running a very fully loaded boat plus knee blocks so there is very little space, a Nalgene works fine but anything much bigger doesn't. The lack of space is also why sponges are so critical.