They were all dead.
Coastal Horseshoe Crab. Tan KH. Photo taken in the 1990s.
A few pairs of mating horseshoe crabs were seen. Pasir Ris Park 21 Sep 2013
Merostomata is the name given to a grouping of the extinct Eurypterida (sea scorpions) and the Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups.