I've done survey flights for a state Department of Wildlife. They entail flying over lakes with an observer, in the most cost-effective airplane the contractor owns. You fly 500-1000 feet a.g.l. while the observer counts fishermen in different areas of the lake.
It's nice because you can fly on days when flight instruction may not be possible, due to ceilings lower than a couple of thousand feet. The time builds relatively quickly also.
Contact your state's Fish and Game, Department of Natural Resources, etc. office to learn who handles the contracts, if there are any in your state.
Minimum pilot qualifications where I performed these flights was just Commercial A.S.E.L.