Beaches and Fishing in Japan

Hello all,

I’m planning a trip to Japan this upcoming September/October and we’ll be staying for a few days near Ito in Izu Peninsula, we found some cool fishing spots nearby so we’re hoping to fish (at least try) on some of the days.

I’ve searched on a few sources online but want to avoid any confusion and potential trouble with local authorities, so I need your help on the following points:

* The sources I’ve found mentions for saltwater fishing (coast, piers, etc) it should be all right without a need of a fishing license/permit – is this a national guideline or can vary from Prefecture to Prefecture?
* For rivers, lakes and such it is mentioned that is mandatory of a permit/license with the possibility of a 1-day permit to be issued – is there website where we can check who can issue a license depending on the area I want to fish?

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As a final note, aside from fishing we’re hoping to go swimming on a few beaches – however it will be outside the official “beach season” – can we get in trouble for such? (We’re not planning to go off to a random cliff or body of water but a designated beach out of the beach season).
I’ve checked a few beaches rules and guidelines but found no mention of off-season swimming.

Thanks!