At the moment, the LAPL does not include floatplane operation, but that is high on the list for change; IAOPA has just pressed EASA about this (again) as the working group hadn't yet come up with any proposal. It will now be dealt with by another rule making task force.
LAPL floatplane operation is also a strong wish from certain Nordic countries, so we will continue to nudge EASA to come up with a solution.
The UK CAA has amended the regulations, so that any licence with single engine piston privileges may be used to fly microlight aeroplanes, provided that the pilot has received the relevant differences training
The NPPL can include floatplane operation for both microlight and SSEA aeroplanes, but it may not be used to fly 'EASA' aircraft after Apr 2018. To fly both SSEA and Microlight aeroplanes requires separate class ratings, but hours on either type may count towards revalidation of both ratings.