How to build a toy exploring boat?
Well, clearly you cannot use that cheap toy to do what you want. The first task you have is to gather all the equipment you want to go into this craft. Obviously, you will want to get the smallest, lightest versions possible, because money seems to not be the issue here. Once you have all your equipment, now the boat becomes just a housing for all that stuff that must keep it afloat. You can relatively easily calculate the amount of water you would need to displace to carry it all, and that will give you the minimum dimensions of your boat. The secret will be to develop air-tight chambers to provide the maximum buoyancy in the least space. I do not understand the need for a “water tight place to put findings”. Won’t the findings be retrieved from the water? It would seem that water ingress would not be an issue here. If you are worried about excessive water egress, then this would be a simple issue to solve, using a sealed, spring-hinged door that the claw would drop your findings into
