WONDERBOOM

Ultimate Ears makes rugged speakers. I've had mine fall around a bit though never from a bike. I am not sure if any other company makes speakers that rugged. Tribit Stormbox Lava floats on water but it's huge for a bike. A UE Wonderboom or Wonderboom 2 might be better I think? Check them and the other speakers out. They're also mud resistant, have some shock resistance and float. The Wonderboom also has this lovely ring so you can hang it. Maybe they're just what you're looking for.

I’m a big fan of UE, my wonderboom has been through hell, lost in the snow till spring, floated a good chunk of a river without me, fell off a truck onto concrete, and daily showers for several years. The only thing is that the bungee strap is kinda broken but it still holds up

I have both the Bose Bluetooth speaker and the smaller Ultimate Ears Wonderboom. The Bose sound is the best but the Wonderboom is excellent for the price.

We have six in our family 2 x Mega 2 x Boom 2 1 x Boom 3 1 x Wonderboom

I love my wonderboom idk why nobody seems to reccomend it

I have a Wonderboom and it's great.

This brand is apparently frowned upon in this sub but I bring a pair of UE Wonderbooms with me when I travel and they're perfect for what you are looking for. Very affordable, very compact, very rugged, and they pair in stereo.

They are definitely nowhere near the top of the list if sound quality is a high priority, but OP said they were looking for something compact and rugged for travel that you can pair in stereo. For the price the Wonderboom accomplishes that pretty well IMO. At home I'm an audiophile that has spent way too much money on semi-high end equipment, but on the road the Wonderbooms are great for what I need - two of them are a pretty well-executed package for that purpose, and they don't cost a lot.

If you like Ultimate Ears speakers (durability, design, etc.) there are some good options and today is a really good day to make a purchase because there are deals. I always recommend that people get two speakers and use them paired in stereo, rather than spending the same amount of money on single speaker. It depends on your use case though - if you typically are moving around a lot when listening then having a stereo pair is less important. It seems like ruggedness and “seaworthyness” are important to you and that makes UE a good option even though the sound quality and bass output aren’t the best - what about size/form factor? I have both the Everboom (bigger) and the Wonderboom (smaller). That’s where I would start. If you move around a lot and don’t want to carry two speakers the Everboom is a good bet if you’re okay with the size (it’s bigger than the Megablast but still very portable). Everyone I’ve recommended the Wonderboom to has been very happy and it’s very affordable.