Well obviously the Aquamarina apartment complex wanted to have it's own beach so they covered a concrete slab with sand and put sunbeds on the adjacent jetty and there you have it. During the week it is very, very quiet largely due to the alternatives in the area - Patalavaca's beach and Anfi beach.
There's some nice views if you grab a sunbed on the jetty and it's generally peaceful. Usually the locals gather on the lower level as there's an area they can put their towels where the steps are to get into the water. There's not enough sand to make it comfortable doing the towel on the sand thing but it's nice to have I guess if you live in Aquamarina though I personally would walk the five minutes along the promenade to get to Anfi beach.
There's a couple of nice restaurants close by and of course lots more plus shops at Anfi. The map shows you how to get to Anfi then Aquamarina is five minutes walk round the corner.