It says that "concerns have been raised with us regarding potential non-compliance and, as a consequence, we have started to conduct a thorough review of those concerns, including the evidentiary basis for, and credibility of, any allegations of non-compliance, alongside a general membership-wide review.
"In defining the scope of the review we are maintaining a focus upon transfers, historic or recent, for members who were registered in the 2018 membership year and those who hold current membership.
"This will include an ongoing check of membership and transfer records to establish whether or not a player has moved to Great Britain to play water polo from a nation where the transfer rules are applicable.
"Where competitions are upcoming or ongoing, notably the British Championships and the inter-regions, members are reminded of the need for compliance and all players should hold a relevant transfer certificate having transferred into the country from abroad. Otherwise they, and the club which they represent, could be subject to sanction."
The transfer window operated by LEN opens again on June 1. The full Swim England statement can be found at https://www.swimming.org/waterpolo/water-polo-transfer-information/