Deep sea portholes are usually cones of acrylic that seat right into a port in the hull [0] [0]https://www.researchgate.net/publication/340442621_Prediction_of

Deep sea portholes are usually cones of acrylic that seat right into a port in the hull [0] [0]https://www.researchgate.net/publication/340442621_Prediction_of_the_service_life_of_deep-sea_conical_acrylic_portholes_at_designing https://www.researchgate.net/publication/340442621_Predictio...