I weigh 205 lbs without gear and the BF5000 does not pull me anywhere near 3.75 mphs. I am however very pleased with the BF5000's power and performance and it has remarkably improved my quality of diving especially given the price. My dive buddy and I take them on trips, dive boats and often just from shore. I'm in S. California which means 7mm full body wetsuit with hood, booties and gloves, 20 lbs of weight plus all the customary dive gear. With all of the extra weight, the BF5000 still rocks.
In terms of their speed estimate, they include an asterik with it if I remember correctly. On a trip to Grand Cayman, my dive buddy had his girlfriend try it out in snorkel gear. I'd estimate her weight at 120 lbs. The BF5000 pulled her much faster than it did him as evidenced by them both using one side by side and him being unable to keep up.
And to all the haters out there who are hung up on the manufacturers claims, we hear you and we who own them don't care. Get over it already. If you want a scooter that pulls you 3+ mph, then spend $5000+. If you want one that greatly enhances your recreational diving, one that is easy to travel with, one that doesn't get in the way when it's not in use, one that only takes a couple hours to charge and one that is affordable, then the BladeFish 5000 is your scooter. Try lugging around any other scooter with one finger on one hand - good luck.
The vast majority of folks who buy these are very pleased.
For the person that says it only lasts on high speed for 10 minutes or less, I'd like to ask you some questions out of curiosity. Are you topping off the battery right before you depart to your dive destination or are you charging it several nights in advance and then taking it out. Does the battery indicator show solid green before you unplug it? When you enter the water and begin using it, how fast does the battery indicator go from green, to flashing green, to red to flashing red? When you take the plug out and are not charging it, does the battery indicator light stay on or does it immediately turn off?