Complex sentence: On arrival at the wreck site, they found very heavy seas breaking over the "Ulrica" forward of the mizzen mast, and the crew had taken refuge in the aft house and the mizzen rigging.
Split into simpler sentences: On arrival at the wreck site, they found very heavy seas breaking over the "Ulrica" forward of the mizzen mast. The crew had taken refuge in the aft house and the mizzen rigging.