This is a pool torpedo just like the ones I played with as a kid. Using a brim is advised because there is not much surface area in contact with the print bed. This model should also be printed using a high infill (75% ish depending on infill type, perimeters and such) to achieve neutral buoyancy. The volume of the torpedo is 115.2 (cm^3), so play with infill and perimeters until the printed weight shows roughly 120 (g) (my torpedo came out about 5 (g) lighter than predicted by slicer). I also suggest using 5 or more perimeters to decrease the likelihood of water infiltration.