Just gonna throw in my 2c worth here.
My store and I have been selling High end Electric skateboards (Evolve, Boosted, Fiik, Mellow, Tranzite and DOT), high powered electric bikes (Stealth Electric Bikes, Solarbike and Evolve) and Foil Drive since as far back as 2010.
Back in the day, we used Lead Acid in the early Fiik boards, then came Lithium ... Absolute game changer for energy and weight. Many brands came and went, and we dealt only with high end brands. We did try a couple of cheap Chinese knock off skateboards to evaluate as they were so much cheaper than the big names coming from Australia, USA, Germany etc. The lessons learned over the last 15 years of being in the Lithium powered toys is YOU GET WHAT YOU PAY FOR!
Hi quality electronics and Lithium batteries cost money, especially when it's designed to be used in and under the water. Knowing what I know, I would NEVER buy cheap Chinese Lithium powered products and keep them inside my house. I had a customer who lost his house in a Lithium fire started by a cheap Chinese scooter. His insurance did NOT cover his loss and he lost EVERYTHING! Starting from scratch in late fifties

Respect and appreciate the costs of designing and building something the right way, there are standards for a reason. Paying more for the best gear is buying peace of mind, known performance, reliability and insurance against the possibility of total loss. I appreciate some people simply can't afford it, but they run the risk buying cheap. I'm risk averse as I could not afford to replace everything in the event of a fire from a cheap toy.
Please be aware of the danger and take this into account when thinking of purchasing Lithium powered water toys especially.
DM