Tesoro / Laser Videos
The Cscope 4pi is a very capable beach machine very popular and cheap for its performance,
The sand shark, the difference being, is fully waterproof which is handy for Wading in surf/heavy rain ect, its a lot more expensive also, if u can afford a sand shark and plan on doing plenty of serious beach detecting all weathers, I would personally opt for that one just because its more versatile, don't feel raw performance is much different really.
Just my opinon. Hope this Helps alittle.