Complex sentence: And under current UK laws, anyone on that water without permission from the riparian owner is trespassing (which is a civil offence) and this may incur a fine or possibly a court injunction to prevent further trespassing.
Split into simpler sentences: And under current UK laws, anyone on that water without permission from the riparian owner is trespassing. This is a civil offence, and may incur a fine or possibly a court injunction to prevent further trespassing.