Cast nets can be a very valuable tool or they can be very frustrating. You need to choose the right cast net for your application.
One of the biggest mistakes I see is someone throwing a 6' net with 1/4" mesh net in 10 feet of water. They say "we can see the bait and we are making good throws but we are not catching any".
The reason for this is they need a bigger, heavier net.
When choosing a net you need to know these 2 things.
1. What depth of water are you planning to net your bait in?
2. What size bait are you trying to catch?
0' to 3' of water
If you are in shallow water you can get away with a smaller, lighter net. I would recommend a 6' - 8' net with a 3/8" mesh. You can change your mesh size to fit the type of bait you are after.
3' to 8' of water
If you are in 3' to 8' of water I would recommend a 8', 10', or 12' net. Again the mesh size depends on the size bait you are after. I would keep the mesh size between 3/8" mesh to 5/8" mesh.
Deeper than 8' of water
If you are in deep water(8'+) you need to have a 10' to 12' net with 1/2" to 3/4" mesh depending on the size of bait. Also your net needs to have 1.5 lbs per foot of weight to allow it to sink fast.
Keep in mind that your net will get heavy after a few throws. So the bigger the net the heavier it is.