When To Go · Destination Guide
Boso Peninsula
From Tateyama shark encounters to Katsuura macro reefs, just beyond Tokyo.
When To Go · Destination Guide
From Tateyama shark encounters to Katsuura macro reefs, just beyond Tokyo.
When to go
Boso does not have a single universally best diving month.
Best overall window
Plan around operator go/no-go decisions.
Outside that window
Dive water can remain warmer; September and October face typhoon, swell and visibility variability.
Start with the overall answer, then switch only when scuba, freedive, snorkel, or topside timing changes the trip in a meaningful way.
The overall row stays visible so you can compare it against the currently selected scope.
| Scope | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall | Overall - Jan: Best | Overall - Feb: Best | Overall - Mar: Best | Overall - Apr: More variable | Overall - May: More variable | Overall - Jun: Good | Overall - Jul: More variable | Overall - Aug: More variable | Overall - Sep: More variable | Overall - Oct: More variable | Overall - Nov: Good | Overall - Dec: Good |
These do not replace the overall planner. Use them only if a specific animal or event is driving your trip dates.
Banded houndsharks and red stingrays at Ito
Best for Scuba
Year-round
BOMMIE describes frequent operator-provisioned encounters at Ito Shark City year-round.
Japanese cormorants near Ito
Best for Scuba
Jan to Apr
JNTO and BOMMIE describe possible diving seabirds from January to early April, a seasonal observation rather than a promised encounter.
Ito grouper behavior
Best for Scuba
Jun to Aug
BOMMIE reports a summer period when large grouper courtship may be visible at the managed site; do not approach or disturb animals.
Nishikawana pelagic fish and eagle rays
Best for Scuba
May to Oct
JNTO notes schooling fish begin around May and possible eagle-ray aggregations.
Namegawa seasonal small fauna
Best for Scuba
Dec to Jun
JNTO describes Shinbama nudibranchs and seasonal cold-water fish within this range.
Built from climate references, access rules, and destination operators. Wildlife timing and route flexibility can shift year to year.