This is not Halicarcinus ovatus it is more likely Ozius deplanatus but the image quality is very poor but definitely not Halicarcinus ovatus the carapace shape the chelae shape is entirely wrong for that species
I note that this observation is placed in the NatureMapr Category "Sea Spiders" (class Pycnogonida). Its correct placement is among the crabs (Subphylum Crustacea, Order Decapoda), at <Ozius deplanatus> .