gr = Import["c:\DolphinSharkBox.obj" ];
Graphics3D[gr[[1]]]

grc = Import["... \DophinSharkBox.obj",  "GraphicsComplex"];
Graphics3D[grc]

polygonsc = Join @@ (Normal[grc] /.
     HoldPattern[VertexNormals -> _] :> Sequence[]);
polygonsc = polygonsc /. Polygon -> Sequence;
edgesc =  DeleteDuplicates[UndirectedEdge @@@ Map[ToString,
     Select[Subsets[polygonsc, {2}], Intersection @@ # =!= {} &], {-2}]];

cc =  Map[ToExpression, ConnectedComponents[Graph[edgesc]], {-1}];
Through@{Length@# &, Tally[Length /@ #] &}@ cc
(* {41, {{3804, 1}, {952, 1}, {288, 2}, {38, 24}, {28, 12}, {6, 1}}} *)

Graph[edgesc, VertexStyle -> White, VertexSize -> .005, VertexShapeFunction -> "Point",
     EdgeStyle -> Directive[Opacity[.5], Thin, Hue[.35, .5, .8]],
     Background -> Black, EdgeShapeFunction -> (Line[#1] &), ImageSize -> 600]

Graphics3D[({EdgeForm[], Hue[RandomReal[]], Polygon@#} & /@ cc), Lighting ->"Neutral"]

Graphics3D[({EdgeForm[], Hue[RandomReal[]], Polygon@# }&/@cc[[;;2]]), Lighting -> "Neutral"]

Graphics3D[({EdgeForm[],Hue[RandomReal[]],Polygon@#}&/@ cc[[3;;-2]]), Lighting -> "Neutral"]