Water pressure an salinity sensor connected to arduino I am trying to design a project that Arduino would have connected water and salinity sensor, would be packed in a special box be droped into ocean up to 500 meters. What sensors should I use and how should they be conencted. I assume that I would need professional equipment, not chineese stuff from ebay.
Hardware needs to be able to work under 50*C and up to 50bar

Update:

Budget is about up to 400 pounds for sensors.
Resolution of pressure 0 to 100 bar
Resolution of salinity doesnt matter so much. Few percents of mistake, just to measure it somehow
I suggest that you look for a sensor from Honeywell. The problem is that the pressure is very high for a board mounted sensor and the atmospheric pressure is varying. The board mounted sensors measure a maximum of 10 bar.  It is not clear what accuracy you require. Is there a connection to the surface? If so you should measure differential pressure between the seabed and the surface.  Can you be content with a maximum depth of 100 m? 

I don't think salinity varies much offshore so it might not be worth measuring.