The country that has the cleanest sea is Europe.
Croatia Europe is considered to have the cleanest sea and has the most cleanest swimming spots located along the Adriatic coastline.
Croatia Europe ranks high in water quality assessments and a large percentage of their coastal waters are classified as being excellent for swimming.
The cleanest ocean in the US is the Schoolhouse Beach on Washington Island In Wisconsin.
The schoolhouse beach is located in Door County, Wisconsin and is a scenic and underrated vacation destination.
The schoolhouse beach features a rocky limestone shoreline, a popular swimming spot and views of Washington Harbor.
The shores of schoolhouse beach are made up of small limestone rocks which have been polished by glaciers and years of erosion from Lake Michigan.
Taking a rock home from schoolhouse beach is said to bring bad luck and can get you up to $250.00 fine per each stolen rock.
Oceans are also considered to be dirtier than pools.
Oceans are large bodies of water which can be contaminated by plastics, agricultural runoff, sewage etc.
Pools are often regularly treated and cleaned with chlorine which keeps them clean.
Bacteria can thrive in the oceans although the saltiness of the ocean can sterilize it someone.
Pools are also safer than oceans as oceans can pose some dangers such as jellyfish, sharks, other sea creatures and even waves and riptides that are unpredictable and can threaten even the strongest of swimmers.
The ocean is sanitary to swim in.
For example the vast majority of ocean waters such as along the coast of Los Angeles County meet State ocean water quality standards.
The only exceptions are areas that are adjacent to or in front of discharging storm drains and after major rainstorms.
Swimming in the ocean is significantly more challenging than swimming in a pool or most other places because you must contend with waves, the change of the tide, the slope of the beach, and strong currents that may be present even when the surface of the ocean appears calm.