Complex sentence: They described it as being brown, 25--30 feet long, with rough skin, three dorsal humps rising above the loch's surface, and a head a foot wide, held out of the water.
Split into simpler sentences: They described it as being brown, 25--30 feet long, and with rough skin. It had three humps rising above the loch's surface, and a head a foot wide, held out of the water.