Is this speaker suitable for use at the beach or in rainy conditions?

Yes. It has an IP66 all-weather rating, making it water-resistant and sandproof for use at the beach, on trails, or in the rain.

How long can the speaker play on a full charge?

The rechargeable battery provides up to 10 hours of playtime.

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Ion iSP156 Uber Boom All-Weather Bluetooth-Enabled Wireless Portable Bluetooth Speaker with Lights and Stereo-Link - IP66 All Weather - 40W (Black)

ON SOUND CONTROL APP Customize audio and lighting
BLUETOOTH 5.0 ENABLED Stream and control your music wirelessly
HIGH-POWER 40-WATT SOUND SYSTEM Dual 2.25” full-range speakers and 2 passive radiators deliver lifelike sound
MULTI-COLORED LIGHTS Woofers glow in multiple colors and dance to the beat
IP66 WATER-RESISTANT/SANDPROOF Safe for beach, trail, and rain
RECHARGEABLE 10-HOUR BATTERY Delivers long-lasting fun
WIRELESS STEREO-LINK Wirelessly connects 1 additional Uber Boom speaker
microSD ® CARD PLAYBACK Conveniently plays material recorded on other devices
BUILT-IN MICROPHONE Provides hands-free call answering
AUX INPUT Easily connect non-Bluetooth devices