From photo it is not clear whether it is multi-cellular algae or angiosperm. Therefore, Based on its habitat, i.e. marine or fresh water, consult a plant taxonomist from your area.
Yes the top photo definitely looks like a bryophyte, and if so needs at least a hand lens and a good local bryophyte key. What specific environment was it taken from? The bottom photo looks like an alga and if so would need a microscope and local key.
To know the species you should look at samples under a microscope. If the samples were from a European river, I would probably say Amblystegium riparium for the moss and Cladophora sp. in the case of the algae. However, I have to say they aren’t typical samples and I won’t ensure the species without passing the samples under the microscope.
You can dry the moss by putting it in a paper envelope, and send it to a specialist. To conserve the algae, it is necessary to put it in alcohol (approximately 65%)