Just a quick question.

Quick answer: NO.

Mixing salt water with concrete is not advised. The concrete will not set up properly and will crumble very easily.

There is a lot of information on this subject if you search "cement mixed with salt water". I was in the Navy Seabees and never heard of any attempts to do that but it sounds like they are experimenting with specially designed cements for use with salt water now. Probably very expensive cements.