Meet Heron: an unmanned surface vessel with a portable design, shallow profile, and built-in GPS that lets you perform a wide variety of research projects. This USV is ready for developers. It has dual payloads for submerged and above water sensors.
As this video shows, you can combine a Heron with an automated water sampler for efficient marine surface water sampling. Heron has a max speed of 3.3 kn / 1.7 m/s and max payload of 10kg. The above video shows how this automated water sampling robot works.