Topside and Weather deck

Topside noun - (usually plural) weather deck; the part of a ship's hull that is above the waterline.

Weather deck and topside are semantically related. In some cases you can use "Weather deck" instead a noun "Topside".

Weather deck noun - Upper deck having no overhead protection from the weather, but sheltering the deck below.

Topside and weather deck are semantically related. Sometimes you can replace term "Topside" with "Weather deck", this terms are similar.