Whether a beach can be walked on, and how you are entitled to reach it, depends on rules that vary substantially between jurisdictions and that are frequently misrepresented by whoever owns the land behind.
This is a general description rather than legal advice, and the position in any specific place is a matter for local rules.
The general shape of the law
Most legal systems distinguish between the land behind a beach and the shore itself.
A common approach treats the area between certain tidal marks as held in trust for the public, meaning it cannot be privately owned and public use for certain purposes is protected.
Where the boundary falls differs. Some jurisdictions draw it at the mean high water line, others at the high tide line, and the practical difference can be a substantial width of beach.
Some go considerably further, guaranteeing public access to the entire beach regardless of who owns the adjoining land.
Which means the same physical situation produces different answers in different places, and assumptions carried from one do not transfer.
The access problem, which is separate
The distinction that matters practically.
A beach can be public while every route to it crosses private land.
Which produces a legally public beach that is effectively private, reachable only by boat or by a long walk along the shore.
Several jurisdictions have addressed this by requiring public access points at intervals, or by preserving historic routes, or by conditioning development permission on providing access.
Disputes over blocked or obstructed access routes are common and have produced substantial litigation in a number of places.
The signage problem
Where the practical difficulty sits.
Signs asserting private beach or no access appear in places where the beach is legally public and the access is legally protected.
Some are honest errors and some are deliberate.
Campaign organisations in several jurisdictions specifically document and challenge these, and local authorities frequently publish maps of protected access points precisely because the signage is unreliable.
Which means checking an official source before concluding a beach is closed is worthwhile, and it is generally a map published by a coastal authority rather than anything at the location.
What public access generally permits
Even where rights exist, they are not unlimited.
Passage along the shore is the most commonly protected activity.
Fishing, swimming and navigation are frequently protected, sometimes as the original basis of the doctrine.
Camping, fires, vehicles and commercial activity are commonly restricted or prohibited regardless of access rights.
And the rights generally do not extend to crossing private land to reach the shore, which is the access question and is governed separately.
The erosion complication
An issue that has become more significant.
Where the boundary is defined by a tidal line, the boundary moves as the shoreline does.
Erosion moves it landward, which can extinguish private land and expand public beach. Accretion does the reverse.
Coastal armouring built to protect property can prevent the beach from migrating, which over time eliminates the public beach entirely — the water reaches the wall and there is nothing between.
This is a live policy conflict in many coastal jurisdictions, between protecting property and preserving public shoreline, and there is no arrangement that does both.
What to check before relying on access
Practical steps.
The relevant coastal authority's published access map, which exists in many jurisdictions and is authoritative.
Local authority information about designated access points and parking.
And, where the position is genuinely unclear, choosing somewhere unambiguous rather than testing it, since a dispute on a holiday is not worth winning.
The practical courtesy
Separate from the legal position.
Where access crosses or passes close to homes, being quiet, keeping to the route, not parking obstructively and taking litter away addresses most of the friction.
A substantial proportion of access disputes are driven by behaviour rather than by principle, and the places where relations are worst are generally the ones where visitors have given cause.
Which is worth bearing in mind by anybody exercising a right that other people have worked to preserve.
Drones, dogs and fires
Three activities regulated separately from access and frequently prohibited.
Drone operation is restricted near people, near wildlife and in protected areas, with rules varying by jurisdiction and enforced.
Dogs are prohibited on many beaches seasonally, generally during the main visitor months, and permitted outside them.
Fires are prohibited on most beaches and permitted in designated areas on some, with restrictions tightening in dry conditions.
All three are locally posted and all three attract enforcement, since they are the activities that generate complaints.
Parking as the real constraint
Where access is most effectively limited in practice.
A public beach reachable only by a road with no parking is publicly accessible in theory and not in practice.
Restricted resident-only parking near beaches is common and has been challenged in some jurisdictions as an indirect restriction on access.
Which means checking parking provision before travelling to a beach is as important as checking access, and public access points generally have designated parking that is published alongside them.