Osaka Prefectural Triathlon Association members dove into the Outer Eastern Moat of Osaka Castle on September 22nd, 2016 to test conditions for swimming. Swimming is prohibited according to the local council, making this the first ever official swim in the castle moat. Special permission was granted by Osaka City, and members of Osaka Life Saving Association were there to observe members during their session. What a great feeling to be the first people in modern history to explore the area by swimming in it! The consensus was favorable: there was no smell, no taste and (obviously) no waves. The water in the moat was incredibly clear and perfect for swimming. Water temperature was a bit higher than the outside air and swimmers felt warm upon initial entry.
As they swam down towards the south side of the moat, the amount of water plants growing from the bottom to the surface steadily increased. By the time they approached the south end of the moat, they were unable to continue swimming as plant growth became quite hazardous. Not to worry, all plant growth will be completely removed prior to the event’s commencement in June 2017. Water plants aside, swimmers were at ease in the water, feeling confident that conditions were ideal for holding the swim event at the 2017 Osaka Castle Triathlon.
Osaka castle has several moats, both inner and outer. The swim takes place in the Outer Eastern Moat
This particular moat is fed by natural ground water reservoirs with a water level 2 metres higher than surrounding waterways, thus ensuring no runoff from external sources. A naturally occuring growth of freshwater weed “aoko” is abundant. Testing of moat water quality has yielded encouraging results as shown in the report summary below.
Outside temp: 23
Water temp: 26
Depth: 2.5-3m (bank depth 10ml to 2.5m, middle area approx 3m)
Water quality summary: odor-none, taste-none, surface oil-none, murkiness-some, colour-clear
Bottom: 20cm gravel/pebbles
Weed growth: considerable (We will remove weeds.)
Aquatic life: freshwater jellyfish (harmless) “Craspedacusta Sowerbii” Not present through the summer months, May-Sep. Various species of fish 10-20cm in length. Japanese Pond Turtle sightings.
Submerged obstacles: green algae