def check_water(pdb_input):
    """
    Given a pdb file checks if it contains water molecules.
    :param pdb_input: pdb input file
    :return: True or False
    """
    checker = False
    with open(pdb_input) as pdb:
        for line in pdb:
            if "HETATM" in line:
                if line.split()[3] == "HOH":
                    print("Your pdb file contains water molecules")
                    checker = True
                    break
    return checker